Line data Source code
1 : // Monocypher version 4.0.2
2 : //
3 : // This file is dual-licensed. Choose whichever licence you want from
4 : // the two licences listed below.
5 : //
6 : // The first licence is a regular 2-clause BSD licence. The second licence
7 : // is the CC-0 from Creative Commons. It is intended to release Monocypher
8 : // to the public domain. The BSD licence serves as a fallback option.
9 : //
10 : // SPDX-License-Identifier: BSD-2-Clause OR CC0-1.0
11 : //
12 : // ------------------------------------------------------------------------
13 : //
14 : // Copyright (c) 2017-2020, Loup Vaillant
15 : // All rights reserved.
16 : //
17 : //
18 : // Redistribution and use in source and binary forms, with or without
19 : // modification, are permitted provided that the following conditions are
20 : // met:
21 : //
22 : // 1. Redistributions of source code must retain the above copyright
23 : // notice, this list of conditions and the following disclaimer.
24 : //
25 : // 2. Redistributions in binary form must reproduce the above copyright
26 : // notice, this list of conditions and the following disclaimer in the
27 : // documentation and/or other materials provided with the
28 : // distribution.
29 : //
30 : // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
31 : // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
32 : // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
33 : // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
34 : // HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
35 : // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
36 : // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
37 : // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
38 : // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
39 : // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
40 : // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
41 : //
42 : // ------------------------------------------------------------------------
43 : //
44 : // Written in 2017-2020 by Loup Vaillant
45 : //
46 : // To the extent possible under law, the author(s) have dedicated all copyright
47 : // and related neighboring rights to this software to the public domain
48 : // worldwide. This software is distributed without any warranty.
49 : //
50 : // You should have received a copy of the CC0 Public Domain Dedication along
51 : // with this software. If not, see
52 : // <https://creativecommons.org/publicdomain/zero/1.0/>
53 :
54 : #include "passgen/monocypher.h"
55 :
56 : #ifdef MONOCYPHER_CPP_NAMESPACE
57 : namespace MONOCYPHER_CPP_NAMESPACE {
58 : #endif
59 :
60 : /////////////////
61 : /// Utilities ///
62 : /////////////////
63 : #define FOR_T(type, i, start, end) for (type i = (start); i < (end); i++)
64 : #define FOR(i, start, end) FOR_T(size_t, i, start, end)
65 : #define COPY(dst, src, size) FOR(_i_, 0, size) (dst)[_i_] = (src)[_i_]
66 : #define ZERO(buf, size) FOR(_i_, 0, size) (buf)[_i_] = 0
67 : #define WIPE_CTX(ctx) passgen_wipe(ctx , sizeof(*(ctx)))
68 : #define WIPE_BUFFER(buffer) passgen_wipe(buffer, sizeof(buffer))
69 : #define MIN(a, b) ((a) <= (b) ? (a) : (b))
70 : #define MAX(a, b) ((a) >= (b) ? (a) : (b))
71 :
72 : typedef int8_t i8;
73 : typedef uint8_t u8;
74 : typedef int16_t i16;
75 : typedef uint32_t u32;
76 : typedef int32_t i32;
77 : typedef int64_t i64;
78 : typedef uint64_t u64;
79 :
80 : static const u8 zero[128] = {0};
81 :
82 : // returns the smallest positive integer y such that
83 : // (x + y) % pow_2 == 0
84 : // Basically, y is the "gap" missing to align x.
85 : // Only works when pow_2 is a power of 2.
86 : // Note: we use ~x+1 instead of -x to avoid compiler warnings
87 39 : static size_t gap(size_t x, size_t pow_2)
88 : {
89 39 : return (~x + 1) & (pow_2 - 1);
90 : }
91 :
92 0 : static u32 load24_le(const u8 s[3])
93 : {
94 : return
95 0 : ((u32)s[0] << 0) |
96 0 : ((u32)s[1] << 8) |
97 0 : ((u32)s[2] << 16);
98 : }
99 :
100 1856 : static u32 load32_le(const u8 s[4])
101 : {
102 : return
103 1856 : ((u32)s[0] << 0) |
104 1856 : ((u32)s[1] << 8) |
105 3712 : ((u32)s[2] << 16) |
106 1856 : ((u32)s[3] << 24);
107 : }
108 :
109 879 : static u64 load64_le(const u8 s[8])
110 : {
111 879 : return load32_le(s) | ((u64)load32_le(s+4) << 32);
112 : }
113 :
114 2841 : static void store32_le(u8 out[4], u32 in)
115 : {
116 2841 : out[0] = in & 0xff;
117 2841 : out[1] = (in >> 8) & 0xff;
118 2841 : out[2] = (in >> 16) & 0xff;
119 2841 : out[3] = (in >> 24) & 0xff;
120 2841 : }
121 :
122 636 : static void store64_le(u8 out[8], u64 in)
123 : {
124 636 : store32_le(out , (u32)in );
125 636 : store32_le(out + 4, in >> 32);
126 636 : }
127 :
128 21 : static void load32_le_buf (u32 *dst, const u8 *src, size_t size) {
129 119 : FOR(i, 0, size) { dst[i] = load32_le(src + i*4); }
130 21 : }
131 99 : static void load64_le_buf (u64 *dst, const u8 *src, size_t size) {
132 978 : FOR(i, 0, size) { dst[i] = load64_le(src + i*8); }
133 99 : }
134 0 : static void store32_le_buf(u8 *dst, const u32 *src, size_t size) {
135 0 : FOR(i, 0, size) { store32_le(dst + i*4, src[i]); }
136 0 : }
137 65 : static void store64_le_buf(u8 *dst, const u64 *src, size_t size) {
138 701 : FOR(i, 0, size) { store64_le(dst + i*8, src[i]); }
139 65 : }
140 :
141 60416 : static u64 rotr64(u64 x, u64 n) { return (x >> n) ^ (x << (64 - n)); }
142 31040 : static u32 rotl32(u32 x, u32 n) { return (x << n) ^ (x >> (32 - n)); }
143 :
144 0 : static int neq0(u64 diff)
145 : {
146 : // constant time comparison to zero
147 : // return diff != 0 ? -1 : 0
148 0 : u64 half = (diff >> 32) | ((u32)diff);
149 0 : return (1 & ((half - 1) >> 32)) - 1;
150 : }
151 :
152 0 : static u64 x16(const u8 a[16], const u8 b[16])
153 : {
154 0 : return (load64_le(a + 0) ^ load64_le(b + 0))
155 0 : | (load64_le(a + 8) ^ load64_le(b + 8));
156 : }
157 0 : static u64 x32(const u8 a[32],const u8 b[32]){return x16(a,b)| x16(a+16, b+16);}
158 0 : static u64 x64(const u8 a[64],const u8 b[64]){return x32(a,b)| x32(a+32, b+32);}
159 0 : int passgen_verify16(const u8 a[16], const u8 b[16]){ return neq0(x16(a, b)); }
160 0 : int passgen_verify32(const u8 a[32], const u8 b[32]){ return neq0(x32(a, b)); }
161 0 : int passgen_verify64(const u8 a[64], const u8 b[64]){ return neq0(x64(a, b)); }
162 :
163 429151 : void passgen_wipe(void *secret, size_t size)
164 : {
165 429151 : volatile u8 *v_secret = (u8*)secret;
166 15831275 : ZERO(v_secret, size);
167 429151 : }
168 :
169 : /////////////////
170 : /// Chacha 20 ///
171 : /////////////////
172 : #define QUARTERROUND(a, b, c, d) \
173 : a += b; d = rotl32(d ^ a, 16); \
174 : c += d; b = rotl32(b ^ c, 12); \
175 : a += b; d = rotl32(d ^ a, 8); \
176 : c += d; b = rotl32(b ^ c, 7)
177 :
178 97 : static void chacha20_rounds(u32 out[16], const u32 in[16])
179 : {
180 : // The temporary variables make Chacha20 10% faster.
181 97 : u32 t0 = in[ 0]; u32 t1 = in[ 1]; u32 t2 = in[ 2]; u32 t3 = in[ 3];
182 97 : u32 t4 = in[ 4]; u32 t5 = in[ 5]; u32 t6 = in[ 6]; u32 t7 = in[ 7];
183 97 : u32 t8 = in[ 8]; u32 t9 = in[ 9]; u32 t10 = in[10]; u32 t11 = in[11];
184 97 : u32 t12 = in[12]; u32 t13 = in[13]; u32 t14 = in[14]; u32 t15 = in[15];
185 :
186 1067 : FOR (i, 0, 10) { // 20 rounds, 2 rounds per loop.
187 970 : QUARTERROUND(t0, t4, t8 , t12); // column 0
188 970 : QUARTERROUND(t1, t5, t9 , t13); // column 1
189 970 : QUARTERROUND(t2, t6, t10, t14); // column 2
190 970 : QUARTERROUND(t3, t7, t11, t15); // column 3
191 970 : QUARTERROUND(t0, t5, t10, t15); // diagonal 0
192 970 : QUARTERROUND(t1, t6, t11, t12); // diagonal 1
193 970 : QUARTERROUND(t2, t7, t8 , t13); // diagonal 2
194 970 : QUARTERROUND(t3, t4, t9 , t14); // diagonal 3
195 : }
196 97 : out[ 0] = t0; out[ 1] = t1; out[ 2] = t2; out[ 3] = t3;
197 97 : out[ 4] = t4; out[ 5] = t5; out[ 6] = t6; out[ 7] = t7;
198 97 : out[ 8] = t8; out[ 9] = t9; out[10] = t10; out[11] = t11;
199 97 : out[12] = t12; out[13] = t13; out[14] = t14; out[15] = t15;
200 97 : }
201 :
202 : static const u8 *chacha20_constant = (const u8*)"expand 32-byte k"; // 16 bytes
203 :
204 0 : void passgen_chacha20_h(u8 out[32], const u8 key[32], const u8 in [16])
205 : {
206 : u32 block[16];
207 0 : load32_le_buf(block , chacha20_constant, 4);
208 0 : load32_le_buf(block + 4, key , 8);
209 0 : load32_le_buf(block + 12, in , 4);
210 :
211 0 : chacha20_rounds(block, block);
212 :
213 : // prevent reversal of the rounds by revealing only half of the buffer.
214 0 : store32_le_buf(out , block , 4); // constant
215 0 : store32_le_buf(out+16, block+12, 4); // counter and nonce
216 0 : WIPE_BUFFER(block);
217 0 : }
218 :
219 7 : u64 passgen_chacha20_djb(u8 *cipher_text, const u8 *plain_text,
220 : size_t text_size, const u8 key[32], const u8 nonce[8],
221 : u64 ctr)
222 : {
223 : u32 input[16];
224 7 : load32_le_buf(input , chacha20_constant, 4);
225 7 : load32_le_buf(input + 4, key , 8);
226 7 : load32_le_buf(input + 14, nonce , 2);
227 7 : input[12] = (u32) ctr;
228 7 : input[13] = (u32)(ctr >> 32);
229 :
230 : // Whole blocks
231 : u32 pool[16];
232 7 : size_t nb_blocks = text_size >> 6;
233 103 : FOR (i, 0, nb_blocks) {
234 96 : chacha20_rounds(pool, input);
235 96 : if (plain_text != 0) {
236 0 : FOR (j, 0, 16) {
237 0 : u32 p = pool[j] + input[j];
238 0 : store32_le(cipher_text, p ^ load32_le(plain_text));
239 0 : cipher_text += 4;
240 0 : plain_text += 4;
241 : }
242 : } else {
243 1632 : FOR (j, 0, 16) {
244 1536 : u32 p = pool[j] + input[j];
245 1536 : store32_le(cipher_text, p);
246 1536 : cipher_text += 4;
247 : }
248 : }
249 96 : input[12]++;
250 96 : if (input[12] == 0) {
251 0 : input[13]++;
252 : }
253 : }
254 7 : text_size &= 63;
255 :
256 : // Last (incomplete) block
257 7 : if (text_size > 0) {
258 1 : if (plain_text == 0) {
259 1 : plain_text = zero;
260 : }
261 1 : chacha20_rounds(pool, input);
262 : u8 tmp[64];
263 17 : FOR (i, 0, 16) {
264 16 : store32_le(tmp + i*4, pool[i] + input[i]);
265 : }
266 8 : FOR (i, 0, text_size) {
267 7 : cipher_text[i] = tmp[i] ^ plain_text[i];
268 : }
269 1 : WIPE_BUFFER(tmp);
270 : }
271 7 : ctr = input[12] + ((u64)input[13] << 32) + (text_size > 0);
272 :
273 7 : WIPE_BUFFER(pool);
274 7 : WIPE_BUFFER(input);
275 7 : return ctr;
276 : }
277 :
278 0 : u32 passgen_chacha20_ietf(u8 *cipher_text, const u8 *plain_text,
279 : size_t text_size,
280 : const u8 key[32], const u8 nonce[12], u32 ctr)
281 : {
282 0 : u64 big_ctr = ctr + ((u64)load32_le(nonce) << 32);
283 0 : return (u32)passgen_chacha20_djb(cipher_text, plain_text, text_size,
284 0 : key, nonce + 4, big_ctr);
285 : }
286 :
287 0 : u64 passgen_chacha20_x(u8 *cipher_text, const u8 *plain_text,
288 : size_t text_size,
289 : const u8 key[32], const u8 nonce[24], u64 ctr)
290 : {
291 : u8 sub_key[32];
292 0 : passgen_chacha20_h(sub_key, key, nonce);
293 0 : ctr = passgen_chacha20_djb(cipher_text, plain_text, text_size,
294 0 : sub_key, nonce + 16, ctr);
295 0 : WIPE_BUFFER(sub_key);
296 0 : return ctr;
297 : }
298 :
299 : /////////////////
300 : /// Poly 1305 ///
301 : /////////////////
302 :
303 : // h = (h + c) * r
304 : // preconditions:
305 : // ctx->h <= 4_ffffffff_ffffffff_ffffffff_ffffffff
306 : // ctx->r <= 0ffffffc_0ffffffc_0ffffffc_0fffffff
307 : // end <= 1
308 : // Postcondition:
309 : // ctx->h <= 4_ffffffff_ffffffff_ffffffff_ffffffff
310 0 : static void poly_blocks(passgen_poly1305_ctx *ctx, const u8 *in,
311 : size_t nb_blocks, unsigned end)
312 : {
313 : // Local all the things!
314 0 : const u32 r0 = ctx->r[0];
315 0 : const u32 r1 = ctx->r[1];
316 0 : const u32 r2 = ctx->r[2];
317 0 : const u32 r3 = ctx->r[3];
318 0 : const u32 rr0 = (r0 >> 2) * 5; // lose 2 bits...
319 0 : const u32 rr1 = (r1 >> 2) + r1; // rr1 == (r1 >> 2) * 5
320 0 : const u32 rr2 = (r2 >> 2) + r2; // rr1 == (r2 >> 2) * 5
321 0 : const u32 rr3 = (r3 >> 2) + r3; // rr1 == (r3 >> 2) * 5
322 0 : const u32 rr4 = r0 & 3; // ...recover 2 bits
323 0 : u32 h0 = ctx->h[0];
324 0 : u32 h1 = ctx->h[1];
325 0 : u32 h2 = ctx->h[2];
326 0 : u32 h3 = ctx->h[3];
327 0 : u32 h4 = ctx->h[4];
328 :
329 0 : FOR (i, 0, nb_blocks) {
330 : // h + c, without carry propagation
331 0 : const u64 s0 = (u64)h0 + load32_le(in); in += 4;
332 0 : const u64 s1 = (u64)h1 + load32_le(in); in += 4;
333 0 : const u64 s2 = (u64)h2 + load32_le(in); in += 4;
334 0 : const u64 s3 = (u64)h3 + load32_le(in); in += 4;
335 0 : const u32 s4 = h4 + end;
336 :
337 : // (h + c) * r, without carry propagation
338 0 : const u64 x0 = s0*r0+ s1*rr3+ s2*rr2+ s3*rr1+ s4*rr0;
339 0 : const u64 x1 = s0*r1+ s1*r0 + s2*rr3+ s3*rr2+ s4*rr1;
340 0 : const u64 x2 = s0*r2+ s1*r1 + s2*r0 + s3*rr3+ s4*rr2;
341 0 : const u64 x3 = s0*r3+ s1*r2 + s2*r1 + s3*r0 + s4*rr3;
342 0 : const u32 x4 = s4*rr4;
343 :
344 : // partial reduction modulo 2^130 - 5
345 0 : const u32 u5 = x4 + (x3 >> 32); // u5 <= 7ffffff5
346 0 : const u64 u0 = (u5 >> 2) * 5 + (x0 & 0xffffffff);
347 0 : const u64 u1 = (u0 >> 32) + (x1 & 0xffffffff) + (x0 >> 32);
348 0 : const u64 u2 = (u1 >> 32) + (x2 & 0xffffffff) + (x1 >> 32);
349 0 : const u64 u3 = (u2 >> 32) + (x3 & 0xffffffff) + (x2 >> 32);
350 0 : const u32 u4 = (u3 >> 32) + (u5 & 3); // u4 <= 4
351 :
352 : // Update the hash
353 0 : h0 = u0 & 0xffffffff;
354 0 : h1 = u1 & 0xffffffff;
355 0 : h2 = u2 & 0xffffffff;
356 0 : h3 = u3 & 0xffffffff;
357 0 : h4 = u4;
358 : }
359 0 : ctx->h[0] = h0;
360 0 : ctx->h[1] = h1;
361 0 : ctx->h[2] = h2;
362 0 : ctx->h[3] = h3;
363 0 : ctx->h[4] = h4;
364 0 : }
365 :
366 0 : void passgen_poly1305_init(passgen_poly1305_ctx *ctx, const u8 key[32])
367 : {
368 0 : ZERO(ctx->h, 5); // Initial hash is zero
369 0 : ctx->c_idx = 0;
370 : // load r and pad (r has some of its bits cleared)
371 0 : load32_le_buf(ctx->r , key , 4);
372 0 : load32_le_buf(ctx->pad, key+16, 4);
373 0 : FOR (i, 0, 1) { ctx->r[i] &= 0x0fffffff; }
374 0 : FOR (i, 1, 4) { ctx->r[i] &= 0x0ffffffc; }
375 0 : }
376 :
377 0 : void passgen_poly1305_update(passgen_poly1305_ctx *ctx,
378 : const u8 *message, size_t message_size)
379 : {
380 : // Avoid undefined NULL pointer increments with empty messages
381 0 : if (message_size == 0) {
382 0 : return;
383 : }
384 :
385 : // Align ourselves with block boundaries
386 0 : size_t aligned = MIN(gap(ctx->c_idx, 16), message_size);
387 0 : FOR (i, 0, aligned) {
388 0 : ctx->c[ctx->c_idx] = *message;
389 0 : ctx->c_idx++;
390 0 : message++;
391 0 : message_size--;
392 : }
393 :
394 : // If block is complete, process it
395 0 : if (ctx->c_idx == 16) {
396 0 : poly_blocks(ctx, ctx->c, 1, 1);
397 0 : ctx->c_idx = 0;
398 : }
399 :
400 : // Process the message block by block
401 0 : size_t nb_blocks = message_size >> 4;
402 0 : poly_blocks(ctx, message, nb_blocks, 1);
403 0 : message += nb_blocks << 4;
404 0 : message_size &= 15;
405 :
406 : // remaining bytes (we never complete a block here)
407 0 : FOR (i, 0, message_size) {
408 0 : ctx->c[ctx->c_idx] = message[i];
409 0 : ctx->c_idx++;
410 : }
411 : }
412 :
413 0 : void passgen_poly1305_final(passgen_poly1305_ctx *ctx, u8 mac[16])
414 : {
415 : // Process the last block (if any)
416 : // We move the final 1 according to remaining input length
417 : // (this will add less than 2^130 to the last input block)
418 0 : if (ctx->c_idx != 0) {
419 0 : ZERO(ctx->c + ctx->c_idx, 16 - ctx->c_idx);
420 0 : ctx->c[ctx->c_idx] = 1;
421 0 : poly_blocks(ctx, ctx->c, 1, 0);
422 : }
423 :
424 : // check if we should subtract 2^130-5 by performing the
425 : // corresponding carry propagation.
426 0 : u64 c = 5;
427 0 : FOR (i, 0, 4) {
428 0 : c += ctx->h[i];
429 0 : c >>= 32;
430 : }
431 0 : c += ctx->h[4];
432 0 : c = (c >> 2) * 5; // shift the carry back to the beginning
433 : // c now indicates how many times we should subtract 2^130-5 (0 or 1)
434 0 : FOR (i, 0, 4) {
435 0 : c += (u64)ctx->h[i] + ctx->pad[i];
436 0 : store32_le(mac + i*4, (u32)c);
437 0 : c = c >> 32;
438 : }
439 0 : WIPE_CTX(ctx);
440 0 : }
441 :
442 0 : void passgen_poly1305(u8 mac[16], const u8 *message,
443 : size_t message_size, const u8 key[32])
444 : {
445 : passgen_poly1305_ctx ctx;
446 0 : passgen_poly1305_init (&ctx, key);
447 0 : passgen_poly1305_update(&ctx, message, message_size);
448 0 : passgen_poly1305_final (&ctx, mac);
449 0 : }
450 :
451 : ////////////////
452 : /// BLAKE2 b ///
453 : ////////////////
454 : static const u64 iv[8] = {
455 : 0x6a09e667f3bcc908, 0xbb67ae8584caa73b,
456 : 0x3c6ef372fe94f82b, 0xa54ff53a5f1d36f1,
457 : 0x510e527fade682d1, 0x9b05688c2b3e6c1f,
458 : 0x1f83d9abfb41bd6b, 0x5be0cd19137e2179,
459 : };
460 :
461 72 : static void blake2b_compress(passgen_blake2b_ctx *ctx, int is_last_block)
462 : {
463 : static const u8 sigma[12][16] = {
464 : { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 },
465 : { 14, 10, 4, 8, 9, 15, 13, 6, 1, 12, 0, 2, 11, 7, 5, 3 },
466 : { 11, 8, 12, 0, 5, 2, 15, 13, 10, 14, 3, 6, 7, 1, 9, 4 },
467 : { 7, 9, 3, 1, 13, 12, 11, 14, 2, 6, 5, 10, 4, 0, 15, 8 },
468 : { 9, 0, 5, 7, 2, 4, 10, 15, 14, 1, 11, 12, 6, 8, 3, 13 },
469 : { 2, 12, 6, 10, 0, 11, 8, 3, 4, 13, 7, 5, 15, 14, 1, 9 },
470 : { 12, 5, 1, 15, 14, 13, 4, 10, 0, 7, 6, 3, 9, 2, 8, 11 },
471 : { 13, 11, 7, 14, 12, 1, 3, 9, 5, 0, 15, 4, 8, 6, 2, 10 },
472 : { 6, 15, 14, 9, 11, 3, 0, 8, 12, 2, 13, 7, 1, 4, 10, 5 },
473 : { 10, 2, 8, 4, 7, 6, 1, 5, 15, 11, 9, 14, 3, 12, 13, 0 },
474 : { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 },
475 : { 14, 10, 4, 8, 9, 15, 13, 6, 1, 12, 0, 2, 11, 7, 5, 3 },
476 : };
477 :
478 : // increment input offset
479 72 : u64 *x = ctx->input_offset;
480 72 : size_t y = ctx->input_idx;
481 72 : x[0] += y;
482 72 : if (x[0] < y) {
483 0 : x[1]++;
484 : }
485 :
486 : // init work vector
487 72 : u64 v0 = ctx->hash[0]; u64 v8 = iv[0];
488 72 : u64 v1 = ctx->hash[1]; u64 v9 = iv[1];
489 72 : u64 v2 = ctx->hash[2]; u64 v10 = iv[2];
490 72 : u64 v3 = ctx->hash[3]; u64 v11 = iv[3];
491 72 : u64 v4 = ctx->hash[4]; u64 v12 = iv[4] ^ ctx->input_offset[0];
492 72 : u64 v5 = ctx->hash[5]; u64 v13 = iv[5] ^ ctx->input_offset[1];
493 72 : u64 v6 = ctx->hash[6]; u64 v14 = iv[6] ^ (u64)~(is_last_block - 1);
494 72 : u64 v7 = ctx->hash[7]; u64 v15 = iv[7];
495 :
496 : // mangle work vector
497 72 : u64 *input = ctx->input;
498 : #define BLAKE2_G(a, b, c, d, x, y) \
499 : a += b + x; d = rotr64(d ^ a, 32); \
500 : c += d; b = rotr64(b ^ c, 24); \
501 : a += b + y; d = rotr64(d ^ a, 16); \
502 : c += d; b = rotr64(b ^ c, 63)
503 : #define BLAKE2_ROUND(i) \
504 : BLAKE2_G(v0, v4, v8 , v12, input[sigma[i][ 0]], input[sigma[i][ 1]]); \
505 : BLAKE2_G(v1, v5, v9 , v13, input[sigma[i][ 2]], input[sigma[i][ 3]]); \
506 : BLAKE2_G(v2, v6, v10, v14, input[sigma[i][ 4]], input[sigma[i][ 5]]); \
507 : BLAKE2_G(v3, v7, v11, v15, input[sigma[i][ 6]], input[sigma[i][ 7]]); \
508 : BLAKE2_G(v0, v5, v10, v15, input[sigma[i][ 8]], input[sigma[i][ 9]]); \
509 : BLAKE2_G(v1, v6, v11, v12, input[sigma[i][10]], input[sigma[i][11]]); \
510 : BLAKE2_G(v2, v7, v8 , v13, input[sigma[i][12]], input[sigma[i][13]]); \
511 : BLAKE2_G(v3, v4, v9 , v14, input[sigma[i][14]], input[sigma[i][15]])
512 :
513 : #ifdef BLAKE2_NO_UNROLLING
514 : FOR (i, 0, 12) {
515 : BLAKE2_ROUND(i);
516 : }
517 : #else
518 72 : BLAKE2_ROUND(0); BLAKE2_ROUND(1); BLAKE2_ROUND(2); BLAKE2_ROUND(3);
519 72 : BLAKE2_ROUND(4); BLAKE2_ROUND(5); BLAKE2_ROUND(6); BLAKE2_ROUND(7);
520 72 : BLAKE2_ROUND(8); BLAKE2_ROUND(9); BLAKE2_ROUND(10); BLAKE2_ROUND(11);
521 : #endif
522 :
523 : // update hash
524 72 : ctx->hash[0] ^= v0 ^ v8; ctx->hash[1] ^= v1 ^ v9;
525 72 : ctx->hash[2] ^= v2 ^ v10; ctx->hash[3] ^= v3 ^ v11;
526 72 : ctx->hash[4] ^= v4 ^ v12; ctx->hash[5] ^= v5 ^ v13;
527 72 : ctx->hash[6] ^= v6 ^ v14; ctx->hash[7] ^= v7 ^ v15;
528 72 : }
529 :
530 64 : void passgen_blake2b_keyed_init(passgen_blake2b_ctx *ctx, size_t hash_size,
531 : const u8 *key, size_t key_size)
532 : {
533 : // initial hash
534 576 : COPY(ctx->hash, iv, 8);
535 64 : ctx->hash[0] ^= 0x01010000 ^ (key_size << 8) ^ hash_size;
536 :
537 64 : ctx->input_offset[0] = 0; // beginning of the input, no offset
538 64 : ctx->input_offset[1] = 0; // beginning of the input, no offset
539 64 : ctx->hash_size = hash_size;
540 64 : ctx->input_idx = 0;
541 1088 : ZERO(ctx->input, 16);
542 :
543 : // if there is a key, the first block is that key (padded with zeroes)
544 64 : if (key_size > 0) {
545 0 : u8 key_block[128] = {0};
546 0 : COPY(key_block, key, key_size);
547 : // same as calling passgen_blake2b_update(ctx, key_block , 128)
548 0 : load64_le_buf(ctx->input, key_block, 16);
549 0 : ctx->input_idx = 128;
550 : }
551 64 : }
552 :
553 4 : void passgen_blake2b_init(passgen_blake2b_ctx *ctx, size_t hash_size)
554 : {
555 4 : passgen_blake2b_keyed_init(ctx, hash_size, 0, 0);
556 4 : }
557 :
558 80 : void passgen_blake2b_update(passgen_blake2b_ctx *ctx,
559 : const u8 *message, size_t message_size)
560 : {
561 : // Avoid undefined NULL pointer increments with empty messages
562 80 : if (message_size == 0) {
563 1 : return;
564 : }
565 :
566 : // Align with word boundaries
567 79 : if ((ctx->input_idx & 7) != 0) {
568 12 : size_t nb_bytes = MIN(gap(ctx->input_idx, 8), message_size);
569 12 : size_t word = ctx->input_idx >> 3;
570 12 : size_t byte = ctx->input_idx & 7;
571 56 : FOR (i, 0, nb_bytes) {
572 44 : ctx->input[word] |= (u64)message[i] << ((byte + i) << 3);
573 : }
574 12 : ctx->input_idx += nb_bytes;
575 12 : message += nb_bytes;
576 12 : message_size -= nb_bytes;
577 : }
578 :
579 : // Align with block boundaries (faster than byte by byte)
580 79 : if ((ctx->input_idx & 127) != 0) {
581 15 : size_t nb_words = MIN(gap(ctx->input_idx, 128), message_size) >> 3;
582 15 : load64_le_buf(ctx->input + (ctx->input_idx >> 3), message, nb_words);
583 15 : ctx->input_idx += nb_words << 3;
584 15 : message += nb_words << 3;
585 15 : message_size -= nb_words << 3;
586 : }
587 :
588 : // Process block by block
589 79 : size_t nb_blocks = message_size >> 7;
590 86 : FOR (i, 0, nb_blocks) {
591 7 : if (ctx->input_idx == 128) {
592 7 : blake2b_compress(ctx, 0);
593 : }
594 7 : load64_le_buf(ctx->input, message, 16);
595 7 : message += 128;
596 7 : ctx->input_idx = 128;
597 : }
598 79 : message_size &= 127;
599 :
600 79 : if (message_size != 0) {
601 : // Compress block & flush input buffer as needed
602 75 : if (ctx->input_idx == 128) {
603 1 : blake2b_compress(ctx, 0);
604 1 : ctx->input_idx = 0;
605 : }
606 75 : if (ctx->input_idx == 0) {
607 1105 : ZERO(ctx->input, 16);
608 : }
609 : // Fill remaining words (faster than byte by byte)
610 75 : size_t nb_words = message_size >> 3;
611 75 : load64_le_buf(ctx->input, message, nb_words);
612 75 : ctx->input_idx += nb_words << 3;
613 75 : message += nb_words << 3;
614 75 : message_size -= nb_words << 3;
615 :
616 : // Fill remaining bytes
617 134 : FOR (i, 0, message_size) {
618 59 : size_t word = ctx->input_idx >> 3;
619 59 : size_t byte = ctx->input_idx & 7;
620 59 : ctx->input[word] |= (u64)message[i] << (byte << 3);
621 59 : ctx->input_idx++;
622 : }
623 : }
624 : }
625 :
626 64 : void passgen_blake2b_final(passgen_blake2b_ctx *ctx, u8 *hash)
627 : {
628 64 : blake2b_compress(ctx, 1); // compress the last block
629 64 : size_t hash_size = MIN(ctx->hash_size, 64);
630 64 : size_t nb_words = hash_size >> 3;
631 64 : store64_le_buf(hash, ctx->hash, nb_words);
632 64 : FOR (i, nb_words << 3, hash_size) {
633 0 : hash[i] = (ctx->hash[i >> 3] >> (8 * (i & 7))) & 0xff;
634 : }
635 64 : WIPE_CTX(ctx);
636 64 : }
637 :
638 60 : void passgen_blake2b_keyed(u8 *hash, size_t hash_size,
639 : const u8 *key, size_t key_size,
640 : const u8 *message, size_t message_size)
641 : {
642 : passgen_blake2b_ctx ctx;
643 60 : passgen_blake2b_keyed_init(&ctx, hash_size, key, key_size);
644 60 : passgen_blake2b_update (&ctx, message, message_size);
645 60 : passgen_blake2b_final (&ctx, hash);
646 60 : }
647 :
648 60 : void passgen_blake2b(u8 *hash, size_t hash_size, const u8 *msg, size_t msg_size)
649 : {
650 60 : passgen_blake2b_keyed(hash, hash_size, 0, 0, msg, msg_size);
651 60 : }
652 :
653 : //////////////
654 : /// Argon2 ///
655 : //////////////
656 : // references to R, Z, Q etc. come from the spec
657 :
658 : // Argon2 operates on 1024 byte blocks.
659 : typedef struct { u64 a[128]; } blk;
660 :
661 : // updates a BLAKE2 hash with a 32 bit word, little endian.
662 13 : static void blake_update_32(passgen_blake2b_ctx *ctx, u32 input)
663 : {
664 : u8 buf[4];
665 13 : store32_le(buf, input);
666 13 : passgen_blake2b_update(ctx, buf, 4);
667 13 : WIPE_BUFFER(buf);
668 13 : }
669 :
670 4 : static void blake_update_32_buf(passgen_blake2b_ctx *ctx,
671 : const u8 *buf, u32 size)
672 : {
673 4 : blake_update_32(ctx, size);
674 4 : passgen_blake2b_update(ctx, buf, size);
675 4 : }
676 :
677 :
678 9030 : static void copy_block(blk *o,const blk*in){FOR(i, 0, 128) o->a[i] = in->a[i];}
679 23478 : static void xor_block(blk *o,const blk*in){FOR(i, 0, 128) o->a[i] ^= in->a[i];}
680 :
681 : // Hash with a virtually unlimited digest size.
682 : // Doesn't extract more entropy than the base hash function.
683 : // Mainly used for filling a whole kilobyte block with pseudo-random bytes.
684 : // (One could use a stream cipher with a seed hash as the key, but
685 : // this would introduce another dependency —and point of failure.)
686 3 : static void extended_hash(u8 *digest, u32 digest_size,
687 : const u8 *input , u32 input_size)
688 : {
689 : passgen_blake2b_ctx ctx;
690 3 : passgen_blake2b_init (&ctx, MIN(digest_size, 64));
691 3 : blake_update_32 (&ctx, digest_size);
692 3 : passgen_blake2b_update(&ctx, input, input_size);
693 3 : passgen_blake2b_final (&ctx, digest);
694 :
695 3 : if (digest_size > 64) {
696 : // the conversion to u64 avoids integer overflow on
697 : // ludicrously big hash sizes.
698 2 : u32 r = (u32)(((u64)digest_size + 31) >> 5) - 2;
699 2 : u32 i = 1;
700 2 : u32 in = 0;
701 2 : u32 out = 32;
702 60 : while (i < r) {
703 : // Input and output overlap. This is intentional
704 58 : passgen_blake2b(digest + out, 64, digest + in, 64);
705 58 : i += 1;
706 58 : in += 32;
707 58 : out += 32;
708 : }
709 2 : passgen_blake2b(digest + out, digest_size - (32 * r), digest + in , 64);
710 : }
711 3 : }
712 :
713 : #define LSB(x) ((u64)(u32)x)
714 : #define G(a, b, c, d) \
715 : a += b + ((LSB(a) * LSB(b)) << 1); d ^= a; d = rotr64(d, 32); \
716 : c += d + ((LSB(c) * LSB(d)) << 1); b ^= c; b = rotr64(b, 24); \
717 : a += b + ((LSB(a) * LSB(b)) << 1); d ^= a; d = rotr64(d, 16); \
718 : c += d + ((LSB(c) * LSB(d)) << 1); b ^= c; b = rotr64(b, 63)
719 : #define ROUND(v0, v1, v2, v3, v4, v5, v6, v7, \
720 : v8, v9, v10, v11, v12, v13, v14, v15) \
721 : G(v0, v4, v8, v12); G(v1, v5, v9, v13); \
722 : G(v2, v6, v10, v14); G(v3, v7, v11, v15); \
723 : G(v0, v5, v10, v15); G(v1, v6, v11, v12); \
724 : G(v2, v7, v8, v13); G(v3, v4, v9, v14)
725 :
726 : // Core of the compression function G. Computes Z from R in place.
727 64 : static void g_rounds(blk *b)
728 : {
729 : // column rounds (work_block = Q)
730 576 : for (int i = 0; i < 128; i += 16) {
731 512 : ROUND(b->a[i ], b->a[i+ 1], b->a[i+ 2], b->a[i+ 3],
732 : b->a[i+ 4], b->a[i+ 5], b->a[i+ 6], b->a[i+ 7],
733 : b->a[i+ 8], b->a[i+ 9], b->a[i+10], b->a[i+11],
734 : b->a[i+12], b->a[i+13], b->a[i+14], b->a[i+15]);
735 : }
736 : // row rounds (b = Z)
737 576 : for (int i = 0; i < 16; i += 2) {
738 512 : ROUND(b->a[i ], b->a[i+ 1], b->a[i+ 16], b->a[i+ 17],
739 : b->a[i+32], b->a[i+33], b->a[i+ 48], b->a[i+ 49],
740 : b->a[i+64], b->a[i+65], b->a[i+ 80], b->a[i+ 81],
741 : b->a[i+96], b->a[i+97], b->a[i+112], b->a[i+113]);
742 : }
743 64 : }
744 :
745 : const passgen_argon2_extras passgen_argon2_no_extras = { 0, 0, 0, 0 };
746 :
747 1 : void passgen_argon2(u8 *hash, u32 hash_size, void *work_area,
748 : passgen_argon2_config config,
749 : passgen_argon2_inputs inputs,
750 : passgen_argon2_extras extras)
751 : {
752 1 : const u32 segment_size = config.nb_blocks / config.nb_lanes / 4;
753 1 : const u32 lane_size = segment_size * 4;
754 1 : const u32 nb_blocks = lane_size * config.nb_lanes; // rounding down
755 :
756 : // work area seen as blocks (must be suitably aligned)
757 1 : blk *blocks = (blk*)work_area;
758 : {
759 : u8 initial_hash[72]; // 64 bytes plus 2 words for future hashes
760 : passgen_blake2b_ctx ctx;
761 1 : passgen_blake2b_init (&ctx, 64);
762 1 : blake_update_32 (&ctx, config.nb_lanes ); // p: number of "threads"
763 1 : blake_update_32 (&ctx, hash_size);
764 1 : blake_update_32 (&ctx, config.nb_blocks);
765 1 : blake_update_32 (&ctx, config.nb_passes);
766 1 : blake_update_32 (&ctx, 0x13); // v: version number
767 1 : blake_update_32 (&ctx, config.algorithm); // y: Argon2i, Argon2d...
768 1 : blake_update_32_buf (&ctx, inputs.pass, inputs.pass_size);
769 1 : blake_update_32_buf (&ctx, inputs.salt, inputs.salt_size);
770 1 : blake_update_32_buf (&ctx, extras.key, extras.key_size);
771 1 : blake_update_32_buf (&ctx, extras.ad, extras.ad_size);
772 1 : passgen_blake2b_final(&ctx, initial_hash); // fill 64 first bytes only
773 :
774 : // fill first 2 blocks of each lane
775 : u8 hash_area[1024];
776 2 : FOR_T(u32, l, 0, config.nb_lanes) {
777 3 : FOR_T(u32, i, 0, 2) {
778 2 : store32_le(initial_hash + 64, i); // first additional word
779 2 : store32_le(initial_hash + 68, l); // second additional word
780 2 : extended_hash(hash_area, 1024, initial_hash, 72);
781 2 : load64_le_buf(blocks[l * lane_size + i].a, hash_area, 128);
782 : }
783 : }
784 :
785 1 : WIPE_BUFFER(initial_hash);
786 1 : WIPE_BUFFER(hash_area);
787 : }
788 :
789 : // Argon2i and Argon2id start with constant time indexing
790 1 : int constant_time = config.algorithm != CRYPTO_ARGON2_D;
791 :
792 : // Fill (and re-fill) the rest of the blocks
793 : //
794 : // Note: even though each segment within the same slice can be
795 : // computed in parallel, (one thread per lane), we are computing
796 : // them sequentially, because Monocypher doesn't support threads.
797 : //
798 : // Yet optimal performance (and therefore security) requires one
799 : // thread per lane. The only reason Monocypher supports multiple
800 : // lanes is compatibility.
801 : blk tmp;
802 9 : FOR_T(u32, pass, 0, config.nb_passes) {
803 40 : FOR_T(u32, slice, 0, 4) {
804 : // On the first slice of the first pass,
805 : // blocks 0 and 1 are already filled, hence pass_offset.
806 32 : u32 pass_offset = pass == 0 && slice == 0 ? 2 : 0;
807 32 : u32 slice_offset = slice * segment_size;
808 :
809 : // Argon2id switches back to non-constant time indexing
810 : // after the first two slices of the first pass
811 32 : if (slice == 2 && config.algorithm == CRYPTO_ARGON2_ID) {
812 8 : constant_time = 0;
813 : }
814 :
815 : // Each iteration of the following loop may be performed in
816 : // a separate thread. All segments must be fully completed
817 : // before we start filling the next slice.
818 64 : FOR_T(u32, segment, 0, config.nb_lanes) {
819 : blk index_block;
820 32 : u32 index_ctr = 1;
821 94 : FOR_T (u32, block, pass_offset, segment_size) {
822 : // Current and previous blocks
823 62 : u32 lane_offset = segment * lane_size;
824 62 : blk *segment_start = blocks + lane_offset + slice_offset;
825 62 : blk *current = segment_start + block;
826 62 : blk *previous =
827 31 : block == 0 && slice_offset == 0
828 7 : ? segment_start + lane_size - 1
829 93 : : segment_start + block - 1;
830 :
831 : u64 index_seed;
832 62 : if (constant_time) {
833 2 : if (block == pass_offset || (block % 128) == 0) {
834 : // Fill or refresh deterministic indices block
835 :
836 : // seed the beginning of the block...
837 129 : ZERO(index_block.a, 128);
838 1 : index_block.a[0] = pass;
839 1 : index_block.a[1] = segment;
840 1 : index_block.a[2] = slice;
841 1 : index_block.a[3] = nb_blocks;
842 1 : index_block.a[4] = config.nb_passes;
843 1 : index_block.a[5] = config.algorithm;
844 1 : index_block.a[6] = index_ctr;
845 1 : index_ctr++;
846 :
847 : // ... then shuffle it
848 1 : copy_block(&tmp, &index_block);
849 1 : g_rounds (&index_block);
850 1 : xor_block (&index_block, &tmp);
851 1 : copy_block(&tmp, &index_block);
852 1 : g_rounds (&index_block);
853 1 : xor_block (&index_block, &tmp);
854 : }
855 2 : index_seed = index_block.a[block % 128];
856 : } else {
857 60 : index_seed = previous->a[0];
858 : }
859 :
860 : // Establish the reference set. *Approximately* comprises:
861 : // - The last 3 slices (if they exist yet)
862 : // - The already constructed blocks in the current segment
863 62 : u32 next_slice = ((slice + 1) % 4) * segment_size;
864 62 : u32 window_start = pass == 0 ? 0 : next_slice;
865 62 : u32 nb_segments = pass == 0 ? slice : 3;
866 62 : u64 lane =
867 6 : pass == 0 && slice == 0
868 : ? segment
869 68 : : (index_seed >> 32) % config.nb_lanes;
870 62 : u32 window_size =
871 62 : nb_segments * segment_size +
872 62 : (lane == segment ? block-1 :
873 : block == 0 ? (u32)-1 : 0);
874 :
875 : // Find reference block
876 62 : u64 j1 = index_seed & 0xffffffff; // block selector
877 62 : u64 x = (j1 * j1) >> 32;
878 62 : u64 y = (window_size * x) >> 32;
879 62 : u64 z = (window_size - 1) - y;
880 62 : u64 ref = (window_start + z) % lane_size;
881 62 : u32 index = lane * lane_size + (u32)ref;
882 62 : blk *reference = blocks + index;
883 :
884 : // Shuffle the previous & reference block
885 : // into the current block
886 62 : copy_block(&tmp, previous);
887 62 : xor_block (&tmp, reference);
888 62 : if (pass == 0) { copy_block(current, &tmp); }
889 56 : else { xor_block (current, &tmp); }
890 62 : g_rounds (&tmp);
891 62 : xor_block (current, &tmp);
892 : }
893 : }
894 : }
895 : }
896 :
897 : // Wipe temporary block
898 1 : volatile u64* p = tmp.a;
899 129 : ZERO(p, 128);
900 :
901 : // XOR last blocks of each lane
902 1 : blk *last_block = blocks + lane_size - 1;
903 1 : FOR_T (u32, lane, 1, config.nb_lanes) {
904 0 : blk *next_block = last_block + lane_size;
905 0 : xor_block(next_block, last_block);
906 0 : last_block = next_block;
907 : }
908 :
909 : // Serialize last block
910 : u8 final_block[1024];
911 1 : store64_le_buf(final_block, last_block->a, 128);
912 :
913 : // Wipe work area
914 1 : p = (u64*)work_area;
915 1025 : ZERO(p, 128 * nb_blocks);
916 :
917 : // Hash the very last block with H' into the output hash
918 1 : extended_hash(hash, hash_size, final_block, 1024);
919 1 : WIPE_BUFFER(final_block);
920 1 : }
921 :
922 : ////////////////////////////////////
923 : /// Arithmetic modulo 2^255 - 19 ///
924 : ////////////////////////////////////
925 : // Originally taken from SUPERCOP's ref10 implementation.
926 : // A bit bigger than TweetNaCl, over 4 times faster.
927 :
928 : // field element
929 : typedef i32 fe[10];
930 :
931 : // field constants
932 : //
933 : // fe_one : 1
934 : // sqrtm1 : sqrt(-1)
935 : // d : -121665 / 121666
936 : // D2 : 2 * -121665 / 121666
937 : // lop_x, lop_y: low order point in Edwards coordinates
938 : // ufactor : -sqrt(-1) * 2
939 : // A2 : 486662^2 (A squared)
940 : static const fe fe_one = {1};
941 : static const fe sqrtm1 = {
942 : -32595792, -7943725, 9377950, 3500415, 12389472,
943 : -272473, -25146209, -2005654, 326686, 11406482,
944 : };
945 : static const fe d = {
946 : -10913610, 13857413, -15372611, 6949391, 114729,
947 : -8787816, -6275908, -3247719, -18696448, -12055116,
948 : };
949 : static const fe D2 = {
950 : -21827239, -5839606, -30745221, 13898782, 229458,
951 : 15978800, -12551817, -6495438, 29715968, 9444199,
952 : };
953 : static const fe lop_x = {
954 : 21352778, 5345713, 4660180, -8347857, 24143090,
955 : 14568123, 30185756, -12247770, -33528939, 8345319,
956 : };
957 : static const fe lop_y = {
958 : -6952922, -1265500, 6862341, -7057498, -4037696,
959 : -5447722, 31680899, -15325402, -19365852, 1569102,
960 : };
961 : static const fe ufactor = {
962 : -1917299, 15887451, -18755900, -7000830, -24778944,
963 : 544946, -16816446, 4011309, -653372, 10741468,
964 : };
965 : static const fe A2 = {
966 : 12721188, 3529, 0, 0, 0, 0, 0, 0, 0, 0,
967 : };
968 :
969 0 : static void fe_0(fe h) { ZERO(h , 10); }
970 0 : static void fe_1(fe h) { h[0] = 1; ZERO(h+1, 9); }
971 :
972 0 : static void fe_copy(fe h,const fe f ){FOR(i,0,10) h[i] = f[i]; }
973 0 : static void fe_neg (fe h,const fe f ){FOR(i,0,10) h[i] = -f[i]; }
974 0 : static void fe_add (fe h,const fe f,const fe g){FOR(i,0,10) h[i] = f[i] + g[i];}
975 0 : static void fe_sub (fe h,const fe f,const fe g){FOR(i,0,10) h[i] = f[i] - g[i];}
976 :
977 0 : static void fe_cswap(fe f, fe g, int b)
978 : {
979 0 : i32 mask = -b; // -1 = 0xffffffff
980 0 : FOR (i, 0, 10) {
981 0 : i32 x = (f[i] ^ g[i]) & mask;
982 0 : f[i] = f[i] ^ x;
983 0 : g[i] = g[i] ^ x;
984 : }
985 0 : }
986 :
987 0 : static void fe_ccopy(fe f, const fe g, int b)
988 : {
989 0 : i32 mask = -b; // -1 = 0xffffffff
990 0 : FOR (i, 0, 10) {
991 0 : i32 x = (f[i] ^ g[i]) & mask;
992 0 : f[i] = f[i] ^ x;
993 : }
994 0 : }
995 :
996 :
997 : // Signed carry propagation
998 : // ------------------------
999 : //
1000 : // Let t be a number. It can be uniquely decomposed thus:
1001 : //
1002 : // t = h*2^26 + l
1003 : // such that -2^25 <= l < 2^25
1004 : //
1005 : // Let c = (t + 2^25) / 2^26 (rounded down)
1006 : // c = (h*2^26 + l + 2^25) / 2^26 (rounded down)
1007 : // c = h + (l + 2^25) / 2^26 (rounded down)
1008 : // c = h (exactly)
1009 : // Because 0 <= l + 2^25 < 2^26
1010 : //
1011 : // Let u = t - c*2^26
1012 : // u = h*2^26 + l - h*2^26
1013 : // u = l
1014 : // Therefore, -2^25 <= u < 2^25
1015 : //
1016 : // Additionally, if |t| < x, then |h| < x/2^26 (rounded down)
1017 : //
1018 : // Notations:
1019 : // - In C, 1<<25 means 2^25.
1020 : // - In C, x>>25 means floor(x / (2^25)).
1021 : // - All of the above applies with 25 & 24 as well as 26 & 25.
1022 : //
1023 : //
1024 : // Note on negative right shifts
1025 : // -----------------------------
1026 : //
1027 : // In C, x >> n, where x is a negative integer, is implementation
1028 : // defined. In practice, all platforms do arithmetic shift, which is
1029 : // equivalent to division by 2^26, rounded down. Some compilers, like
1030 : // GCC, even guarantee it.
1031 : //
1032 : // If we ever stumble upon a platform that does not propagate the sign
1033 : // bit (we won't), visible failures will show at the slightest test, and
1034 : // the signed shifts can be replaced by the following:
1035 : //
1036 : // typedef struct { i64 x:39; } s25;
1037 : // typedef struct { i64 x:38; } s26;
1038 : // i64 shift25(i64 x) { s25 s; s.x = ((u64)x)>>25; return s.x; }
1039 : // i64 shift26(i64 x) { s26 s; s.x = ((u64)x)>>26; return s.x; }
1040 : //
1041 : // Current compilers cannot optimise this, causing a 30% drop in
1042 : // performance. Fairly expensive for something that never happens.
1043 : //
1044 : //
1045 : // Precondition
1046 : // ------------
1047 : //
1048 : // |t0| < 2^63
1049 : // |t1|..|t9| < 2^62
1050 : //
1051 : // Algorithm
1052 : // ---------
1053 : // c = t0 + 2^25 / 2^26 -- |c| <= 2^36
1054 : // t0 -= c * 2^26 -- |t0| <= 2^25
1055 : // t1 += c -- |t1| <= 2^63
1056 : //
1057 : // c = t4 + 2^25 / 2^26 -- |c| <= 2^36
1058 : // t4 -= c * 2^26 -- |t4| <= 2^25
1059 : // t5 += c -- |t5| <= 2^63
1060 : //
1061 : // c = t1 + 2^24 / 2^25 -- |c| <= 2^38
1062 : // t1 -= c * 2^25 -- |t1| <= 2^24
1063 : // t2 += c -- |t2| <= 2^63
1064 : //
1065 : // c = t5 + 2^24 / 2^25 -- |c| <= 2^38
1066 : // t5 -= c * 2^25 -- |t5| <= 2^24
1067 : // t6 += c -- |t6| <= 2^63
1068 : //
1069 : // c = t2 + 2^25 / 2^26 -- |c| <= 2^37
1070 : // t2 -= c * 2^26 -- |t2| <= 2^25 < 1.1 * 2^25 (final t2)
1071 : // t3 += c -- |t3| <= 2^63
1072 : //
1073 : // c = t6 + 2^25 / 2^26 -- |c| <= 2^37
1074 : // t6 -= c * 2^26 -- |t6| <= 2^25 < 1.1 * 2^25 (final t6)
1075 : // t7 += c -- |t7| <= 2^63
1076 : //
1077 : // c = t3 + 2^24 / 2^25 -- |c| <= 2^38
1078 : // t3 -= c * 2^25 -- |t3| <= 2^24 < 1.1 * 2^24 (final t3)
1079 : // t4 += c -- |t4| <= 2^25 + 2^38 < 2^39
1080 : //
1081 : // c = t7 + 2^24 / 2^25 -- |c| <= 2^38
1082 : // t7 -= c * 2^25 -- |t7| <= 2^24 < 1.1 * 2^24 (final t7)
1083 : // t8 += c -- |t8| <= 2^63
1084 : //
1085 : // c = t4 + 2^25 / 2^26 -- |c| <= 2^13
1086 : // t4 -= c * 2^26 -- |t4| <= 2^25 < 1.1 * 2^25 (final t4)
1087 : // t5 += c -- |t5| <= 2^24 + 2^13 < 1.1 * 2^24 (final t5)
1088 : //
1089 : // c = t8 + 2^25 / 2^26 -- |c| <= 2^37
1090 : // t8 -= c * 2^26 -- |t8| <= 2^25 < 1.1 * 2^25 (final t8)
1091 : // t9 += c -- |t9| <= 2^63
1092 : //
1093 : // c = t9 + 2^24 / 2^25 -- |c| <= 2^38
1094 : // t9 -= c * 2^25 -- |t9| <= 2^24 < 1.1 * 2^24 (final t9)
1095 : // t0 += c * 19 -- |t0| <= 2^25 + 2^38*19 < 2^44
1096 : //
1097 : // c = t0 + 2^25 / 2^26 -- |c| <= 2^18
1098 : // t0 -= c * 2^26 -- |t0| <= 2^25 < 1.1 * 2^25 (final t0)
1099 : // t1 += c -- |t1| <= 2^24 + 2^18 < 1.1 * 2^24 (final t1)
1100 : //
1101 : // Postcondition
1102 : // -------------
1103 : // |t0|, |t2|, |t4|, |t6|, |t8| < 1.1 * 2^25
1104 : // |t1|, |t3|, |t5|, |t7|, |t9| < 1.1 * 2^24
1105 : #define FE_CARRY \
1106 : i64 c; \
1107 : c = (t0 + ((i64)1<<25)) >> 26; t0 -= c * ((i64)1 << 26); t1 += c; \
1108 : c = (t4 + ((i64)1<<25)) >> 26; t4 -= c * ((i64)1 << 26); t5 += c; \
1109 : c = (t1 + ((i64)1<<24)) >> 25; t1 -= c * ((i64)1 << 25); t2 += c; \
1110 : c = (t5 + ((i64)1<<24)) >> 25; t5 -= c * ((i64)1 << 25); t6 += c; \
1111 : c = (t2 + ((i64)1<<25)) >> 26; t2 -= c * ((i64)1 << 26); t3 += c; \
1112 : c = (t6 + ((i64)1<<25)) >> 26; t6 -= c * ((i64)1 << 26); t7 += c; \
1113 : c = (t3 + ((i64)1<<24)) >> 25; t3 -= c * ((i64)1 << 25); t4 += c; \
1114 : c = (t7 + ((i64)1<<24)) >> 25; t7 -= c * ((i64)1 << 25); t8 += c; \
1115 : c = (t4 + ((i64)1<<25)) >> 26; t4 -= c * ((i64)1 << 26); t5 += c; \
1116 : c = (t8 + ((i64)1<<25)) >> 26; t8 -= c * ((i64)1 << 26); t9 += c; \
1117 : c = (t9 + ((i64)1<<24)) >> 25; t9 -= c * ((i64)1 << 25); t0 += c * 19; \
1118 : c = (t0 + ((i64)1<<25)) >> 26; t0 -= c * ((i64)1 << 26); t1 += c; \
1119 : h[0]=(i32)t0; h[1]=(i32)t1; h[2]=(i32)t2; h[3]=(i32)t3; h[4]=(i32)t4; \
1120 : h[5]=(i32)t5; h[6]=(i32)t6; h[7]=(i32)t7; h[8]=(i32)t8; h[9]=(i32)t9
1121 :
1122 : // Decodes a field element from a byte buffer.
1123 : // mask specifies how many bits we ignore.
1124 : // Traditionally we ignore 1. It's useful for EdDSA,
1125 : // which uses that bit to denote the sign of x.
1126 : // Elligator however uses positive representatives,
1127 : // which means ignoring 2 bits instead.
1128 0 : static void fe_frombytes_mask(fe h, const u8 s[32], unsigned nb_mask)
1129 : {
1130 0 : u32 mask = 0xffffff >> nb_mask;
1131 0 : i64 t0 = load32_le(s); // t0 < 2^32
1132 0 : i64 t1 = load24_le(s + 4) << 6; // t1 < 2^30
1133 0 : i64 t2 = load24_le(s + 7) << 5; // t2 < 2^29
1134 0 : i64 t3 = load24_le(s + 10) << 3; // t3 < 2^27
1135 0 : i64 t4 = load24_le(s + 13) << 2; // t4 < 2^26
1136 0 : i64 t5 = load32_le(s + 16); // t5 < 2^32
1137 0 : i64 t6 = load24_le(s + 20) << 7; // t6 < 2^31
1138 0 : i64 t7 = load24_le(s + 23) << 5; // t7 < 2^29
1139 0 : i64 t8 = load24_le(s + 26) << 4; // t8 < 2^28
1140 0 : i64 t9 = (load24_le(s + 29) & mask) << 2; // t9 < 2^25
1141 0 : FE_CARRY; // Carry precondition OK
1142 0 : }
1143 :
1144 0 : static void fe_frombytes(fe h, const u8 s[32])
1145 : {
1146 0 : fe_frombytes_mask(h, s, 1);
1147 0 : }
1148 :
1149 :
1150 : // Precondition
1151 : // |h[0]|, |h[2]|, |h[4]|, |h[6]|, |h[8]| < 1.1 * 2^25
1152 : // |h[1]|, |h[3]|, |h[5]|, |h[7]|, |h[9]| < 1.1 * 2^24
1153 : //
1154 : // Therefore, |h| < 2^255-19
1155 : // There are two possibilities:
1156 : //
1157 : // - If h is positive, all we need to do is reduce its individual
1158 : // limbs down to their tight positive range.
1159 : // - If h is negative, we also need to add 2^255-19 to it.
1160 : // Or just remove 19 and chop off any excess bit.
1161 0 : static void fe_tobytes(u8 s[32], const fe h)
1162 : {
1163 : i32 t[10];
1164 0 : COPY(t, h, 10);
1165 0 : i32 q = (19 * t[9] + (((i32) 1) << 24)) >> 25;
1166 : // |t9| < 1.1 * 2^24
1167 : // -1.1 * 2^24 < t9 < 1.1 * 2^24
1168 : // -21 * 2^24 < 19 * t9 < 21 * 2^24
1169 : // -2^29 < 19 * t9 + 2^24 < 2^29
1170 : // -2^29 / 2^25 < (19 * t9 + 2^24) / 2^25 < 2^29 / 2^25
1171 : // -16 < (19 * t9 + 2^24) / 2^25 < 16
1172 0 : FOR (i, 0, 5) {
1173 0 : q += t[2*i ]; q >>= 26; // q = 0 or -1
1174 0 : q += t[2*i+1]; q >>= 25; // q = 0 or -1
1175 : }
1176 : // q = 0 iff h >= 0
1177 : // q = -1 iff h < 0
1178 : // Adding q * 19 to h reduces h to its proper range.
1179 0 : q *= 19; // Shift carry back to the beginning
1180 0 : FOR (i, 0, 5) {
1181 0 : t[i*2 ] += q; q = t[i*2 ] >> 26; t[i*2 ] -= q * ((i32)1 << 26);
1182 0 : t[i*2+1] += q; q = t[i*2+1] >> 25; t[i*2+1] -= q * ((i32)1 << 25);
1183 : }
1184 : // h is now fully reduced, and q represents the excess bit.
1185 :
1186 0 : store32_le(s + 0, ((u32)t[0] >> 0) | ((u32)t[1] << 26));
1187 0 : store32_le(s + 4, ((u32)t[1] >> 6) | ((u32)t[2] << 19));
1188 0 : store32_le(s + 8, ((u32)t[2] >> 13) | ((u32)t[3] << 13));
1189 0 : store32_le(s + 12, ((u32)t[3] >> 19) | ((u32)t[4] << 6));
1190 0 : store32_le(s + 16, ((u32)t[5] >> 0) | ((u32)t[6] << 25));
1191 0 : store32_le(s + 20, ((u32)t[6] >> 7) | ((u32)t[7] << 19));
1192 0 : store32_le(s + 24, ((u32)t[7] >> 13) | ((u32)t[8] << 12));
1193 0 : store32_le(s + 28, ((u32)t[8] >> 20) | ((u32)t[9] << 6));
1194 :
1195 0 : WIPE_BUFFER(t);
1196 0 : }
1197 :
1198 : // Precondition
1199 : // -------------
1200 : // |f0|, |f2|, |f4|, |f6|, |f8| < 1.65 * 2^26
1201 : // |f1|, |f3|, |f5|, |f7|, |f9| < 1.65 * 2^25
1202 : //
1203 : // |g0|, |g2|, |g4|, |g6|, |g8| < 1.65 * 2^26
1204 : // |g1|, |g3|, |g5|, |g7|, |g9| < 1.65 * 2^25
1205 0 : static void fe_mul_small(fe h, const fe f, i32 g)
1206 : {
1207 0 : i64 t0 = f[0] * (i64) g; i64 t1 = f[1] * (i64) g;
1208 0 : i64 t2 = f[2] * (i64) g; i64 t3 = f[3] * (i64) g;
1209 0 : i64 t4 = f[4] * (i64) g; i64 t5 = f[5] * (i64) g;
1210 0 : i64 t6 = f[6] * (i64) g; i64 t7 = f[7] * (i64) g;
1211 0 : i64 t8 = f[8] * (i64) g; i64 t9 = f[9] * (i64) g;
1212 : // |t0|, |t2|, |t4|, |t6|, |t8| < 1.65 * 2^26 * 2^31 < 2^58
1213 : // |t1|, |t3|, |t5|, |t7|, |t9| < 1.65 * 2^25 * 2^31 < 2^57
1214 :
1215 0 : FE_CARRY; // Carry precondition OK
1216 0 : }
1217 :
1218 : // Precondition
1219 : // -------------
1220 : // |f0|, |f2|, |f4|, |f6|, |f8| < 1.65 * 2^26
1221 : // |f1|, |f3|, |f5|, |f7|, |f9| < 1.65 * 2^25
1222 : //
1223 : // |g0|, |g2|, |g4|, |g6|, |g8| < 1.65 * 2^26
1224 : // |g1|, |g3|, |g5|, |g7|, |g9| < 1.65 * 2^25
1225 0 : static void fe_mul(fe h, const fe f, const fe g)
1226 : {
1227 : // Everything is unrolled and put in temporary variables.
1228 : // We could roll the loop, but that would make curve25519 twice as slow.
1229 0 : i32 f0 = f[0]; i32 f1 = f[1]; i32 f2 = f[2]; i32 f3 = f[3]; i32 f4 = f[4];
1230 0 : i32 f5 = f[5]; i32 f6 = f[6]; i32 f7 = f[7]; i32 f8 = f[8]; i32 f9 = f[9];
1231 0 : i32 g0 = g[0]; i32 g1 = g[1]; i32 g2 = g[2]; i32 g3 = g[3]; i32 g4 = g[4];
1232 0 : i32 g5 = g[5]; i32 g6 = g[6]; i32 g7 = g[7]; i32 g8 = g[8]; i32 g9 = g[9];
1233 0 : i32 F1 = f1*2; i32 F3 = f3*2; i32 F5 = f5*2; i32 F7 = f7*2; i32 F9 = f9*2;
1234 0 : i32 G1 = g1*19; i32 G2 = g2*19; i32 G3 = g3*19;
1235 0 : i32 G4 = g4*19; i32 G5 = g5*19; i32 G6 = g6*19;
1236 0 : i32 G7 = g7*19; i32 G8 = g8*19; i32 G9 = g9*19;
1237 : // |F1|, |F3|, |F5|, |F7|, |F9| < 1.65 * 2^26
1238 : // |G0|, |G2|, |G4|, |G6|, |G8| < 2^31
1239 : // |G1|, |G3|, |G5|, |G7|, |G9| < 2^30
1240 :
1241 0 : i64 t0 = f0*(i64)g0 + F1*(i64)G9 + f2*(i64)G8 + F3*(i64)G7 + f4*(i64)G6
1242 0 : + F5*(i64)G5 + f6*(i64)G4 + F7*(i64)G3 + f8*(i64)G2 + F9*(i64)G1;
1243 0 : i64 t1 = f0*(i64)g1 + f1*(i64)g0 + f2*(i64)G9 + f3*(i64)G8 + f4*(i64)G7
1244 0 : + f5*(i64)G6 + f6*(i64)G5 + f7*(i64)G4 + f8*(i64)G3 + f9*(i64)G2;
1245 0 : i64 t2 = f0*(i64)g2 + F1*(i64)g1 + f2*(i64)g0 + F3*(i64)G9 + f4*(i64)G8
1246 0 : + F5*(i64)G7 + f6*(i64)G6 + F7*(i64)G5 + f8*(i64)G4 + F9*(i64)G3;
1247 0 : i64 t3 = f0*(i64)g3 + f1*(i64)g2 + f2*(i64)g1 + f3*(i64)g0 + f4*(i64)G9
1248 0 : + f5*(i64)G8 + f6*(i64)G7 + f7*(i64)G6 + f8*(i64)G5 + f9*(i64)G4;
1249 0 : i64 t4 = f0*(i64)g4 + F1*(i64)g3 + f2*(i64)g2 + F3*(i64)g1 + f4*(i64)g0
1250 0 : + F5*(i64)G9 + f6*(i64)G8 + F7*(i64)G7 + f8*(i64)G6 + F9*(i64)G5;
1251 0 : i64 t5 = f0*(i64)g5 + f1*(i64)g4 + f2*(i64)g3 + f3*(i64)g2 + f4*(i64)g1
1252 0 : + f5*(i64)g0 + f6*(i64)G9 + f7*(i64)G8 + f8*(i64)G7 + f9*(i64)G6;
1253 0 : i64 t6 = f0*(i64)g6 + F1*(i64)g5 + f2*(i64)g4 + F3*(i64)g3 + f4*(i64)g2
1254 0 : + F5*(i64)g1 + f6*(i64)g0 + F7*(i64)G9 + f8*(i64)G8 + F9*(i64)G7;
1255 0 : i64 t7 = f0*(i64)g7 + f1*(i64)g6 + f2*(i64)g5 + f3*(i64)g4 + f4*(i64)g3
1256 0 : + f5*(i64)g2 + f6*(i64)g1 + f7*(i64)g0 + f8*(i64)G9 + f9*(i64)G8;
1257 0 : i64 t8 = f0*(i64)g8 + F1*(i64)g7 + f2*(i64)g6 + F3*(i64)g5 + f4*(i64)g4
1258 0 : + F5*(i64)g3 + f6*(i64)g2 + F7*(i64)g1 + f8*(i64)g0 + F9*(i64)G9;
1259 0 : i64 t9 = f0*(i64)g9 + f1*(i64)g8 + f2*(i64)g7 + f3*(i64)g6 + f4*(i64)g5
1260 0 : + f5*(i64)g4 + f6*(i64)g3 + f7*(i64)g2 + f8*(i64)g1 + f9*(i64)g0;
1261 : // t0 < 0.67 * 2^61
1262 : // t1 < 0.41 * 2^61
1263 : // t2 < 0.52 * 2^61
1264 : // t3 < 0.32 * 2^61
1265 : // t4 < 0.38 * 2^61
1266 : // t5 < 0.22 * 2^61
1267 : // t6 < 0.23 * 2^61
1268 : // t7 < 0.13 * 2^61
1269 : // t8 < 0.09 * 2^61
1270 : // t9 < 0.03 * 2^61
1271 :
1272 0 : FE_CARRY; // Everything below 2^62, Carry precondition OK
1273 0 : }
1274 :
1275 : // Precondition
1276 : // -------------
1277 : // |f0|, |f2|, |f4|, |f6|, |f8| < 1.65 * 2^26
1278 : // |f1|, |f3|, |f5|, |f7|, |f9| < 1.65 * 2^25
1279 : //
1280 : // Note: we could use fe_mul() for this, but this is significantly faster
1281 0 : static void fe_sq(fe h, const fe f)
1282 : {
1283 0 : i32 f0 = f[0]; i32 f1 = f[1]; i32 f2 = f[2]; i32 f3 = f[3]; i32 f4 = f[4];
1284 0 : i32 f5 = f[5]; i32 f6 = f[6]; i32 f7 = f[7]; i32 f8 = f[8]; i32 f9 = f[9];
1285 0 : i32 f0_2 = f0*2; i32 f1_2 = f1*2; i32 f2_2 = f2*2; i32 f3_2 = f3*2;
1286 0 : i32 f4_2 = f4*2; i32 f5_2 = f5*2; i32 f6_2 = f6*2; i32 f7_2 = f7*2;
1287 0 : i32 f5_38 = f5*38; i32 f6_19 = f6*19; i32 f7_38 = f7*38;
1288 0 : i32 f8_19 = f8*19; i32 f9_38 = f9*38;
1289 : // |f0_2| , |f2_2| , |f4_2| , |f6_2| , |f8_2| < 1.65 * 2^27
1290 : // |f1_2| , |f3_2| , |f5_2| , |f7_2| , |f9_2| < 1.65 * 2^26
1291 : // |f5_38|, |f6_19|, |f7_38|, |f8_19|, |f9_38| < 2^31
1292 :
1293 0 : i64 t0 = f0 *(i64)f0 + f1_2*(i64)f9_38 + f2_2*(i64)f8_19
1294 0 : + f3_2*(i64)f7_38 + f4_2*(i64)f6_19 + f5 *(i64)f5_38;
1295 0 : i64 t1 = f0_2*(i64)f1 + f2 *(i64)f9_38 + f3_2*(i64)f8_19
1296 0 : + f4 *(i64)f7_38 + f5_2*(i64)f6_19;
1297 0 : i64 t2 = f0_2*(i64)f2 + f1_2*(i64)f1 + f3_2*(i64)f9_38
1298 0 : + f4_2*(i64)f8_19 + f5_2*(i64)f7_38 + f6 *(i64)f6_19;
1299 0 : i64 t3 = f0_2*(i64)f3 + f1_2*(i64)f2 + f4 *(i64)f9_38
1300 0 : + f5_2*(i64)f8_19 + f6 *(i64)f7_38;
1301 0 : i64 t4 = f0_2*(i64)f4 + f1_2*(i64)f3_2 + f2 *(i64)f2
1302 0 : + f5_2*(i64)f9_38 + f6_2*(i64)f8_19 + f7 *(i64)f7_38;
1303 0 : i64 t5 = f0_2*(i64)f5 + f1_2*(i64)f4 + f2_2*(i64)f3
1304 0 : + f6 *(i64)f9_38 + f7_2*(i64)f8_19;
1305 0 : i64 t6 = f0_2*(i64)f6 + f1_2*(i64)f5_2 + f2_2*(i64)f4
1306 0 : + f3_2*(i64)f3 + f7_2*(i64)f9_38 + f8 *(i64)f8_19;
1307 0 : i64 t7 = f0_2*(i64)f7 + f1_2*(i64)f6 + f2_2*(i64)f5
1308 0 : + f3_2*(i64)f4 + f8 *(i64)f9_38;
1309 0 : i64 t8 = f0_2*(i64)f8 + f1_2*(i64)f7_2 + f2_2*(i64)f6
1310 0 : + f3_2*(i64)f5_2 + f4 *(i64)f4 + f9 *(i64)f9_38;
1311 0 : i64 t9 = f0_2*(i64)f9 + f1_2*(i64)f8 + f2_2*(i64)f7
1312 0 : + f3_2*(i64)f6 + f4 *(i64)f5_2;
1313 : // t0 < 0.67 * 2^61
1314 : // t1 < 0.41 * 2^61
1315 : // t2 < 0.52 * 2^61
1316 : // t3 < 0.32 * 2^61
1317 : // t4 < 0.38 * 2^61
1318 : // t5 < 0.22 * 2^61
1319 : // t6 < 0.23 * 2^61
1320 : // t7 < 0.13 * 2^61
1321 : // t8 < 0.09 * 2^61
1322 : // t9 < 0.03 * 2^61
1323 :
1324 0 : FE_CARRY;
1325 0 : }
1326 :
1327 : // Parity check. Returns 0 if even, 1 if odd
1328 0 : static int fe_isodd(const fe f)
1329 : {
1330 : u8 s[32];
1331 0 : fe_tobytes(s, f);
1332 0 : u8 isodd = s[0] & 1;
1333 0 : WIPE_BUFFER(s);
1334 0 : return isodd;
1335 : }
1336 :
1337 : // Returns 1 if equal, 0 if not equal
1338 0 : static int fe_isequal(const fe f, const fe g)
1339 : {
1340 : u8 fs[32];
1341 : u8 gs[32];
1342 0 : fe_tobytes(fs, f);
1343 0 : fe_tobytes(gs, g);
1344 0 : int isdifferent = passgen_verify32(fs, gs);
1345 0 : WIPE_BUFFER(fs);
1346 0 : WIPE_BUFFER(gs);
1347 0 : return 1 + isdifferent;
1348 : }
1349 :
1350 : // Inverse square root.
1351 : // Returns true if x is a square, false otherwise.
1352 : // After the call:
1353 : // isr = sqrt(1/x) if x is a non-zero square.
1354 : // isr = sqrt(sqrt(-1)/x) if x is not a square.
1355 : // isr = 0 if x is zero.
1356 : // We do not guarantee the sign of the square root.
1357 : //
1358 : // Notes:
1359 : // Let quartic = x^((p-1)/4)
1360 : //
1361 : // x^((p-1)/2) = chi(x)
1362 : // quartic^2 = chi(x)
1363 : // quartic = sqrt(chi(x))
1364 : // quartic = 1 or -1 or sqrt(-1) or -sqrt(-1)
1365 : //
1366 : // Note that x is a square if quartic is 1 or -1
1367 : // There are 4 cases to consider:
1368 : //
1369 : // if quartic = 1 (x is a square)
1370 : // then x^((p-1)/4) = 1
1371 : // x^((p-5)/4) * x = 1
1372 : // x^((p-5)/4) = 1/x
1373 : // x^((p-5)/8) = sqrt(1/x) or -sqrt(1/x)
1374 : //
1375 : // if quartic = -1 (x is a square)
1376 : // then x^((p-1)/4) = -1
1377 : // x^((p-5)/4) * x = -1
1378 : // x^((p-5)/4) = -1/x
1379 : // x^((p-5)/8) = sqrt(-1) / sqrt(x)
1380 : // x^((p-5)/8) * sqrt(-1) = sqrt(-1)^2 / sqrt(x)
1381 : // x^((p-5)/8) * sqrt(-1) = -1/sqrt(x)
1382 : // x^((p-5)/8) * sqrt(-1) = -sqrt(1/x) or sqrt(1/x)
1383 : //
1384 : // if quartic = sqrt(-1) (x is not a square)
1385 : // then x^((p-1)/4) = sqrt(-1)
1386 : // x^((p-5)/4) * x = sqrt(-1)
1387 : // x^((p-5)/4) = sqrt(-1)/x
1388 : // x^((p-5)/8) = sqrt(sqrt(-1)/x) or -sqrt(sqrt(-1)/x)
1389 : //
1390 : // Note that the product of two non-squares is always a square:
1391 : // For any non-squares a and b, chi(a) = -1 and chi(b) = -1.
1392 : // Since chi(x) = x^((p-1)/2), chi(a)*chi(b) = chi(a*b) = 1.
1393 : // Therefore a*b is a square.
1394 : //
1395 : // Since sqrt(-1) and x are both non-squares, their product is a
1396 : // square, and we can compute their square root.
1397 : //
1398 : // if quartic = -sqrt(-1) (x is not a square)
1399 : // then x^((p-1)/4) = -sqrt(-1)
1400 : // x^((p-5)/4) * x = -sqrt(-1)
1401 : // x^((p-5)/4) = -sqrt(-1)/x
1402 : // x^((p-5)/8) = sqrt(-sqrt(-1)/x)
1403 : // x^((p-5)/8) = sqrt( sqrt(-1)/x) * sqrt(-1)
1404 : // x^((p-5)/8) * sqrt(-1) = sqrt( sqrt(-1)/x) * sqrt(-1)^2
1405 : // x^((p-5)/8) * sqrt(-1) = sqrt( sqrt(-1)/x) * -1
1406 : // x^((p-5)/8) * sqrt(-1) = -sqrt(sqrt(-1)/x) or sqrt(sqrt(-1)/x)
1407 0 : static int invsqrt(fe isr, const fe x)
1408 : {
1409 : fe t0, t1, t2;
1410 :
1411 : // t0 = x^((p-5)/8)
1412 : // Can be achieved with a simple double & add ladder,
1413 : // but it would be slower.
1414 0 : fe_sq(t0, x);
1415 0 : fe_sq(t1,t0); fe_sq(t1, t1); fe_mul(t1, x, t1);
1416 0 : fe_mul(t0, t0, t1);
1417 0 : fe_sq(t0, t0); fe_mul(t0, t1, t0);
1418 0 : fe_sq(t1, t0); FOR (i, 1, 5) { fe_sq(t1, t1); } fe_mul(t0, t1, t0);
1419 0 : fe_sq(t1, t0); FOR (i, 1, 10) { fe_sq(t1, t1); } fe_mul(t1, t1, t0);
1420 0 : fe_sq(t2, t1); FOR (i, 1, 20) { fe_sq(t2, t2); } fe_mul(t1, t2, t1);
1421 0 : fe_sq(t1, t1); FOR (i, 1, 10) { fe_sq(t1, t1); } fe_mul(t0, t1, t0);
1422 0 : fe_sq(t1, t0); FOR (i, 1, 50) { fe_sq(t1, t1); } fe_mul(t1, t1, t0);
1423 0 : fe_sq(t2, t1); FOR (i, 1, 100) { fe_sq(t2, t2); } fe_mul(t1, t2, t1);
1424 0 : fe_sq(t1, t1); FOR (i, 1, 50) { fe_sq(t1, t1); } fe_mul(t0, t1, t0);
1425 0 : fe_sq(t0, t0); FOR (i, 1, 2) { fe_sq(t0, t0); } fe_mul(t0, t0, x);
1426 :
1427 : // quartic = x^((p-1)/4)
1428 0 : i32 *quartic = t1;
1429 0 : fe_sq (quartic, t0);
1430 0 : fe_mul(quartic, quartic, x);
1431 :
1432 0 : i32 *check = t2;
1433 0 : fe_0 (check); int z0 = fe_isequal(x , check);
1434 0 : fe_1 (check); int p1 = fe_isequal(quartic, check);
1435 0 : fe_neg(check, check ); int m1 = fe_isequal(quartic, check);
1436 0 : fe_neg(check, sqrtm1); int ms = fe_isequal(quartic, check);
1437 :
1438 : // if quartic == -1 or sqrt(-1)
1439 : // then isr = x^((p-1)/4) * sqrt(-1)
1440 : // else isr = x^((p-1)/4)
1441 0 : fe_mul(isr, t0, sqrtm1);
1442 0 : fe_ccopy(isr, t0, 1 - (m1 | ms));
1443 :
1444 0 : WIPE_BUFFER(t0);
1445 0 : WIPE_BUFFER(t1);
1446 0 : WIPE_BUFFER(t2);
1447 0 : return p1 | m1 | z0;
1448 : }
1449 :
1450 : // Inverse in terms of inverse square root.
1451 : // Requires two additional squarings to get rid of the sign.
1452 : //
1453 : // 1/x = x * (+invsqrt(x^2))^2
1454 : // = x * (-invsqrt(x^2))^2
1455 : //
1456 : // A fully optimised exponentiation by p-1 would save 6 field
1457 : // multiplications, but it would require more code.
1458 0 : static void fe_invert(fe out, const fe x)
1459 : {
1460 : fe tmp;
1461 0 : fe_sq(tmp, x);
1462 0 : invsqrt(tmp, tmp);
1463 0 : fe_sq(tmp, tmp);
1464 0 : fe_mul(out, tmp, x);
1465 0 : WIPE_BUFFER(tmp);
1466 0 : }
1467 :
1468 : // trim a scalar for scalar multiplication
1469 0 : void passgen_eddsa_trim_scalar(u8 out[32], const u8 in[32])
1470 : {
1471 0 : COPY(out, in, 32);
1472 0 : out[ 0] &= 248;
1473 0 : out[31] &= 127;
1474 0 : out[31] |= 64;
1475 0 : }
1476 :
1477 : // get bit from scalar at position i
1478 0 : static int scalar_bit(const u8 s[32], int i)
1479 : {
1480 0 : if (i < 0) { return 0; } // handle -1 for sliding windows
1481 0 : return (s[i>>3] >> (i&7)) & 1;
1482 : }
1483 :
1484 : ///////////////
1485 : /// X-25519 /// Taken from SUPERCOP's ref10 implementation.
1486 : ///////////////
1487 0 : static void scalarmult(u8 q[32], const u8 scalar[32], const u8 p[32],
1488 : int nb_bits)
1489 : {
1490 : // computes the scalar product
1491 : fe x1;
1492 0 : fe_frombytes(x1, p);
1493 :
1494 : // computes the actual scalar product (the result is in x2 and z2)
1495 : fe x2, z2, x3, z3, t0, t1;
1496 : // Montgomery ladder
1497 : // In projective coordinates, to avoid divisions: x = X / Z
1498 : // We don't care about the y coordinate, it's only 1 bit of information
1499 0 : fe_1(x2); fe_0(z2); // "zero" point
1500 0 : fe_copy(x3, x1); fe_1(z3); // "one" point
1501 0 : int swap = 0;
1502 0 : for (int pos = nb_bits-1; pos >= 0; --pos) {
1503 : // constant time conditional swap before ladder step
1504 0 : int b = scalar_bit(scalar, pos);
1505 0 : swap ^= b; // xor trick avoids swapping at the end of the loop
1506 0 : fe_cswap(x2, x3, swap);
1507 0 : fe_cswap(z2, z3, swap);
1508 0 : swap = b; // anticipates one last swap after the loop
1509 :
1510 : // Montgomery ladder step: replaces (P2, P3) by (P2*2, P2+P3)
1511 : // with differential addition
1512 0 : fe_sub(t0, x3, z3);
1513 0 : fe_sub(t1, x2, z2);
1514 0 : fe_add(x2, x2, z2);
1515 0 : fe_add(z2, x3, z3);
1516 0 : fe_mul(z3, t0, x2);
1517 0 : fe_mul(z2, z2, t1);
1518 0 : fe_sq (t0, t1 );
1519 0 : fe_sq (t1, x2 );
1520 0 : fe_add(x3, z3, z2);
1521 0 : fe_sub(z2, z3, z2);
1522 0 : fe_mul(x2, t1, t0);
1523 0 : fe_sub(t1, t1, t0);
1524 0 : fe_sq (z2, z2 );
1525 0 : fe_mul_small(z3, t1, 121666);
1526 0 : fe_sq (x3, x3 );
1527 0 : fe_add(t0, t0, z3);
1528 0 : fe_mul(z3, x1, z2);
1529 0 : fe_mul(z2, t1, t0);
1530 : }
1531 : // last swap is necessary to compensate for the xor trick
1532 : // Note: after this swap, P3 == P2 + P1.
1533 0 : fe_cswap(x2, x3, swap);
1534 0 : fe_cswap(z2, z3, swap);
1535 :
1536 : // normalises the coordinates: x == X / Z
1537 0 : fe_invert(z2, z2);
1538 0 : fe_mul(x2, x2, z2);
1539 0 : fe_tobytes(q, x2);
1540 :
1541 0 : WIPE_BUFFER(x1);
1542 0 : WIPE_BUFFER(x2); WIPE_BUFFER(z2); WIPE_BUFFER(t0);
1543 0 : WIPE_BUFFER(x3); WIPE_BUFFER(z3); WIPE_BUFFER(t1);
1544 0 : }
1545 :
1546 0 : void passgen_x25519(u8 raw_shared_secret[32],
1547 : const u8 your_secret_key [32],
1548 : const u8 their_public_key [32])
1549 : {
1550 : // restrict the possible scalar values
1551 : u8 e[32];
1552 0 : passgen_eddsa_trim_scalar(e, your_secret_key);
1553 0 : scalarmult(raw_shared_secret, e, their_public_key, 255);
1554 0 : WIPE_BUFFER(e);
1555 0 : }
1556 :
1557 0 : void passgen_x25519_public_key(u8 public_key[32],
1558 : const u8 secret_key[32])
1559 : {
1560 : static const u8 base_point[32] = {9};
1561 0 : passgen_x25519(public_key, secret_key, base_point);
1562 0 : }
1563 :
1564 : ///////////////////////////
1565 : /// Arithmetic modulo L ///
1566 : ///////////////////////////
1567 : static const u32 L[8] = {
1568 : 0x5cf5d3ed, 0x5812631a, 0xa2f79cd6, 0x14def9de,
1569 : 0x00000000, 0x00000000, 0x00000000, 0x10000000,
1570 : };
1571 :
1572 : // p = a*b + p
1573 0 : static void multiply(u32 p[16], const u32 a[8], const u32 b[8])
1574 : {
1575 0 : FOR (i, 0, 8) {
1576 0 : u64 carry = 0;
1577 0 : FOR (j, 0, 8) {
1578 0 : carry += p[i+j] + (u64)a[i] * b[j];
1579 0 : p[i+j] = (u32)carry;
1580 0 : carry >>= 32;
1581 : }
1582 0 : p[i+8] = (u32)carry;
1583 : }
1584 0 : }
1585 :
1586 0 : static int is_above_l(const u32 x[8])
1587 : {
1588 : // We work with L directly, in a 2's complement encoding
1589 : // (-L == ~L + 1)
1590 0 : u64 carry = 1;
1591 0 : FOR (i, 0, 8) {
1592 0 : carry += (u64)x[i] + (~L[i] & 0xffffffff);
1593 0 : carry >>= 32;
1594 : }
1595 0 : return (int)carry; // carry is either 0 or 1
1596 : }
1597 :
1598 : // Final reduction modulo L, by conditionally removing L.
1599 : // if x < l , then r = x
1600 : // if l <= x 2*l, then r = x-l
1601 : // otherwise the result will be wrong
1602 0 : static void remove_l(u32 r[8], const u32 x[8])
1603 : {
1604 0 : u64 carry = (u64)is_above_l(x);
1605 0 : u32 mask = ~(u32)carry + 1; // carry == 0 or 1
1606 0 : FOR (i, 0, 8) {
1607 0 : carry += (u64)x[i] + (~L[i] & mask);
1608 0 : r[i] = (u32)carry;
1609 0 : carry >>= 32;
1610 : }
1611 0 : }
1612 :
1613 : // Full reduction modulo L (Barrett reduction)
1614 0 : static void mod_l(u8 reduced[32], const u32 x[16])
1615 : {
1616 : static const u32 r[9] = {
1617 : 0x0a2c131b,0xed9ce5a3,0x086329a7,0x2106215d,
1618 : 0xffffffeb,0xffffffff,0xffffffff,0xffffffff,0xf,
1619 : };
1620 : // xr = x * r
1621 0 : u32 xr[25] = {0};
1622 0 : FOR (i, 0, 9) {
1623 0 : u64 carry = 0;
1624 0 : FOR (j, 0, 16) {
1625 0 : carry += xr[i+j] + (u64)r[i] * x[j];
1626 0 : xr[i+j] = (u32)carry;
1627 0 : carry >>= 32;
1628 : }
1629 0 : xr[i+16] = (u32)carry;
1630 : }
1631 : // xr = floor(xr / 2^512) * L
1632 : // Since the result is guaranteed to be below 2*L,
1633 : // it is enough to only compute the first 256 bits.
1634 : // The division is performed by saying xr[i+16]. (16 * 32 = 512)
1635 0 : ZERO(xr, 8);
1636 0 : FOR (i, 0, 8) {
1637 0 : u64 carry = 0;
1638 0 : FOR (j, 0, 8-i) {
1639 0 : carry += xr[i+j] + (u64)xr[i+16] * L[j];
1640 0 : xr[i+j] = (u32)carry;
1641 0 : carry >>= 32;
1642 : }
1643 : }
1644 : // xr = x - xr
1645 0 : u64 carry = 1;
1646 0 : FOR (i, 0, 8) {
1647 0 : carry += (u64)x[i] + (~xr[i] & 0xffffffff);
1648 0 : xr[i] = (u32)carry;
1649 0 : carry >>= 32;
1650 : }
1651 : // Final reduction modulo L (conditional subtraction)
1652 0 : remove_l(xr, xr);
1653 0 : store32_le_buf(reduced, xr, 8);
1654 :
1655 0 : WIPE_BUFFER(xr);
1656 0 : }
1657 :
1658 0 : void passgen_eddsa_reduce(u8 reduced[32], const u8 expanded[64])
1659 : {
1660 : u32 x[16];
1661 0 : load32_le_buf(x, expanded, 16);
1662 0 : mod_l(reduced, x);
1663 0 : WIPE_BUFFER(x);
1664 0 : }
1665 :
1666 : // r = (a * b) + c
1667 0 : void passgen_eddsa_mul_add(u8 r[32],
1668 : const u8 a[32], const u8 b[32], const u8 c[32])
1669 : {
1670 0 : u32 A[8]; load32_le_buf(A, a, 8);
1671 0 : u32 B[8]; load32_le_buf(B, b, 8);
1672 0 : u32 p[16]; load32_le_buf(p, c, 8); ZERO(p + 8, 8);
1673 0 : multiply(p, A, B);
1674 0 : mod_l(r, p);
1675 0 : WIPE_BUFFER(p);
1676 0 : WIPE_BUFFER(A);
1677 0 : WIPE_BUFFER(B);
1678 0 : }
1679 :
1680 : ///////////////
1681 : /// Ed25519 ///
1682 : ///////////////
1683 :
1684 : // Point (group element, ge) in a twisted Edwards curve,
1685 : // in extended projective coordinates.
1686 : // ge : x = X/Z, y = Y/Z, T = XY/Z
1687 : // ge_cached : Yp = X+Y, Ym = X-Y, T2 = T*D2
1688 : // ge_precomp: Z = 1
1689 : typedef struct { fe X; fe Y; fe Z; fe T; } ge;
1690 : typedef struct { fe Yp; fe Ym; fe Z; fe T2; } ge_cached;
1691 : typedef struct { fe Yp; fe Ym; fe T2; } ge_precomp;
1692 :
1693 0 : static void ge_zero(ge *p)
1694 : {
1695 0 : fe_0(p->X);
1696 0 : fe_1(p->Y);
1697 0 : fe_1(p->Z);
1698 0 : fe_0(p->T);
1699 0 : }
1700 :
1701 0 : static void ge_tobytes(u8 s[32], const ge *h)
1702 : {
1703 : fe recip, x, y;
1704 0 : fe_invert(recip, h->Z);
1705 0 : fe_mul(x, h->X, recip);
1706 0 : fe_mul(y, h->Y, recip);
1707 0 : fe_tobytes(s, y);
1708 0 : s[31] ^= fe_isodd(x) << 7;
1709 :
1710 0 : WIPE_BUFFER(recip);
1711 0 : WIPE_BUFFER(x);
1712 0 : WIPE_BUFFER(y);
1713 0 : }
1714 :
1715 : // h = -s, where s is a point encoded in 32 bytes
1716 : //
1717 : // Variable time! Inputs must not be secret!
1718 : // => Use only to *check* signatures.
1719 : //
1720 : // From the specifications:
1721 : // The encoding of s contains y and the sign of x
1722 : // x = sqrt((y^2 - 1) / (d*y^2 + 1))
1723 : // In extended coordinates:
1724 : // X = x, Y = y, Z = 1, T = x*y
1725 : //
1726 : // Note that num * den is a square iff num / den is a square
1727 : // If num * den is not a square, the point was not on the curve.
1728 : // From the above:
1729 : // Let num = y^2 - 1
1730 : // Let den = d*y^2 + 1
1731 : // x = sqrt((y^2 - 1) / (d*y^2 + 1))
1732 : // x = sqrt(num / den)
1733 : // x = sqrt(num^2 / (num * den))
1734 : // x = num * sqrt(1 / (num * den))
1735 : //
1736 : // Therefore, we can just compute:
1737 : // num = y^2 - 1
1738 : // den = d*y^2 + 1
1739 : // isr = invsqrt(num * den) // abort if not square
1740 : // x = num * isr
1741 : // Finally, negate x if its sign is not as specified.
1742 0 : static int ge_frombytes_neg_vartime(ge *h, const u8 s[32])
1743 : {
1744 0 : fe_frombytes(h->Y, s);
1745 0 : fe_1(h->Z);
1746 0 : fe_sq (h->T, h->Y); // t = y^2
1747 0 : fe_mul(h->X, h->T, d ); // x = d*y^2
1748 0 : fe_sub(h->T, h->T, h->Z); // t = y^2 - 1
1749 0 : fe_add(h->X, h->X, h->Z); // x = d*y^2 + 1
1750 0 : fe_mul(h->X, h->T, h->X); // x = (y^2 - 1) * (d*y^2 + 1)
1751 0 : int is_square = invsqrt(h->X, h->X);
1752 0 : if (!is_square) {
1753 0 : return -1; // Not on the curve, abort
1754 : }
1755 0 : fe_mul(h->X, h->T, h->X); // x = sqrt((y^2 - 1) / (d*y^2 + 1))
1756 0 : if (fe_isodd(h->X) == (s[31] >> 7)) {
1757 0 : fe_neg(h->X, h->X);
1758 : }
1759 0 : fe_mul(h->T, h->X, h->Y);
1760 0 : return 0;
1761 : }
1762 :
1763 0 : static void ge_cache(ge_cached *c, const ge *p)
1764 : {
1765 0 : fe_add (c->Yp, p->Y, p->X);
1766 0 : fe_sub (c->Ym, p->Y, p->X);
1767 0 : fe_copy(c->Z , p->Z );
1768 0 : fe_mul (c->T2, p->T, D2 );
1769 0 : }
1770 :
1771 : // Internal buffers are not wiped! Inputs must not be secret!
1772 : // => Use only to *check* signatures.
1773 0 : static void ge_add(ge *s, const ge *p, const ge_cached *q)
1774 : {
1775 : fe a, b;
1776 0 : fe_add(a , p->Y, p->X );
1777 0 : fe_sub(b , p->Y, p->X );
1778 0 : fe_mul(a , a , q->Yp);
1779 0 : fe_mul(b , b , q->Ym);
1780 0 : fe_add(s->Y, a , b );
1781 0 : fe_sub(s->X, a , b );
1782 :
1783 0 : fe_add(s->Z, p->Z, p->Z );
1784 0 : fe_mul(s->Z, s->Z, q->Z );
1785 0 : fe_mul(s->T, p->T, q->T2);
1786 0 : fe_add(a , s->Z, s->T );
1787 0 : fe_sub(b , s->Z, s->T );
1788 :
1789 0 : fe_mul(s->T, s->X, s->Y);
1790 0 : fe_mul(s->X, s->X, b );
1791 0 : fe_mul(s->Y, s->Y, a );
1792 0 : fe_mul(s->Z, a , b );
1793 0 : }
1794 :
1795 : // Internal buffers are not wiped! Inputs must not be secret!
1796 : // => Use only to *check* signatures.
1797 0 : static void ge_sub(ge *s, const ge *p, const ge_cached *q)
1798 : {
1799 : ge_cached neg;
1800 0 : fe_copy(neg.Ym, q->Yp);
1801 0 : fe_copy(neg.Yp, q->Ym);
1802 0 : fe_copy(neg.Z , q->Z );
1803 0 : fe_neg (neg.T2, q->T2);
1804 0 : ge_add(s, p, &neg);
1805 0 : }
1806 :
1807 0 : static void ge_madd(ge *s, const ge *p, const ge_precomp *q, fe a, fe b)
1808 : {
1809 0 : fe_add(a , p->Y, p->X );
1810 0 : fe_sub(b , p->Y, p->X );
1811 0 : fe_mul(a , a , q->Yp);
1812 0 : fe_mul(b , b , q->Ym);
1813 0 : fe_add(s->Y, a , b );
1814 0 : fe_sub(s->X, a , b );
1815 :
1816 0 : fe_add(s->Z, p->Z, p->Z );
1817 0 : fe_mul(s->T, p->T, q->T2);
1818 0 : fe_add(a , s->Z, s->T );
1819 0 : fe_sub(b , s->Z, s->T );
1820 :
1821 0 : fe_mul(s->T, s->X, s->Y);
1822 0 : fe_mul(s->X, s->X, b );
1823 0 : fe_mul(s->Y, s->Y, a );
1824 0 : fe_mul(s->Z, a , b );
1825 0 : }
1826 :
1827 : // Internal buffers are not wiped! Inputs must not be secret!
1828 : // => Use only to *check* signatures.
1829 0 : static void ge_msub(ge *s, const ge *p, const ge_precomp *q, fe a, fe b)
1830 : {
1831 : ge_precomp neg;
1832 0 : fe_copy(neg.Ym, q->Yp);
1833 0 : fe_copy(neg.Yp, q->Ym);
1834 0 : fe_neg (neg.T2, q->T2);
1835 0 : ge_madd(s, p, &neg, a, b);
1836 0 : }
1837 :
1838 0 : static void ge_double(ge *s, const ge *p, ge *q)
1839 : {
1840 0 : fe_sq (q->X, p->X);
1841 0 : fe_sq (q->Y, p->Y);
1842 0 : fe_sq (q->Z, p->Z); // qZ = pZ^2
1843 0 : fe_mul_small(q->Z, q->Z, 2); // qZ = pZ^2 * 2
1844 0 : fe_add(q->T, p->X, p->Y);
1845 0 : fe_sq (s->T, q->T);
1846 0 : fe_add(q->T, q->Y, q->X);
1847 0 : fe_sub(q->Y, q->Y, q->X);
1848 0 : fe_sub(q->X, s->T, q->T);
1849 0 : fe_sub(q->Z, q->Z, q->Y);
1850 :
1851 0 : fe_mul(s->X, q->X , q->Z);
1852 0 : fe_mul(s->Y, q->T , q->Y);
1853 0 : fe_mul(s->Z, q->Y , q->Z);
1854 0 : fe_mul(s->T, q->X , q->T);
1855 0 : }
1856 :
1857 : // 5-bit signed window in cached format (Niels coordinates, Z=1)
1858 : static const ge_precomp b_window[8] = {
1859 : {{25967493,-14356035,29566456,3660896,-12694345,
1860 : 4014787,27544626,-11754271,-6079156,2047605,},
1861 : {-12545711,934262,-2722910,3049990,-727428,
1862 : 9406986,12720692,5043384,19500929,-15469378,},
1863 : {-8738181,4489570,9688441,-14785194,10184609,
1864 : -12363380,29287919,11864899,-24514362,-4438546,},},
1865 : {{15636291,-9688557,24204773,-7912398,616977,
1866 : -16685262,27787600,-14772189,28944400,-1550024,},
1867 : {16568933,4717097,-11556148,-1102322,15682896,
1868 : -11807043,16354577,-11775962,7689662,11199574,},
1869 : {30464156,-5976125,-11779434,-15670865,23220365,
1870 : 15915852,7512774,10017326,-17749093,-9920357,},},
1871 : {{10861363,11473154,27284546,1981175,-30064349,
1872 : 12577861,32867885,14515107,-15438304,10819380,},
1873 : {4708026,6336745,20377586,9066809,-11272109,
1874 : 6594696,-25653668,12483688,-12668491,5581306,},
1875 : {19563160,16186464,-29386857,4097519,10237984,
1876 : -4348115,28542350,13850243,-23678021,-15815942,},},
1877 : {{5153746,9909285,1723747,-2777874,30523605,
1878 : 5516873,19480852,5230134,-23952439,-15175766,},
1879 : {-30269007,-3463509,7665486,10083793,28475525,
1880 : 1649722,20654025,16520125,30598449,7715701,},
1881 : {28881845,14381568,9657904,3680757,-20181635,
1882 : 7843316,-31400660,1370708,29794553,-1409300,},},
1883 : {{-22518993,-6692182,14201702,-8745502,-23510406,
1884 : 8844726,18474211,-1361450,-13062696,13821877,},
1885 : {-6455177,-7839871,3374702,-4740862,-27098617,
1886 : -10571707,31655028,-7212327,18853322,-14220951,},
1887 : {4566830,-12963868,-28974889,-12240689,-7602672,
1888 : -2830569,-8514358,-10431137,2207753,-3209784,},},
1889 : {{-25154831,-4185821,29681144,7868801,-6854661,
1890 : -9423865,-12437364,-663000,-31111463,-16132436,},
1891 : {25576264,-2703214,7349804,-11814844,16472782,
1892 : 9300885,3844789,15725684,171356,6466918,},
1893 : {23103977,13316479,9739013,-16149481,817875,
1894 : -15038942,8965339,-14088058,-30714912,16193877,},},
1895 : {{-33521811,3180713,-2394130,14003687,-16903474,
1896 : -16270840,17238398,4729455,-18074513,9256800,},
1897 : {-25182317,-4174131,32336398,5036987,-21236817,
1898 : 11360617,22616405,9761698,-19827198,630305,},
1899 : {-13720693,2639453,-24237460,-7406481,9494427,
1900 : -5774029,-6554551,-15960994,-2449256,-14291300,},},
1901 : {{-3151181,-5046075,9282714,6866145,-31907062,
1902 : -863023,-18940575,15033784,25105118,-7894876,},
1903 : {-24326370,15950226,-31801215,-14592823,-11662737,
1904 : -5090925,1573892,-2625887,2198790,-15804619,},
1905 : {-3099351,10324967,-2241613,7453183,-5446979,
1906 : -2735503,-13812022,-16236442,-32461234,-12290683,},},
1907 : };
1908 :
1909 : // Incremental sliding windows (left to right)
1910 : // Based on Roberto Maria Avanzi[2005]
1911 : typedef struct {
1912 : i16 next_index; // position of the next signed digit
1913 : i8 next_digit; // next signed digit (odd number below 2^window_width)
1914 : u8 next_check; // point at which we must check for a new window
1915 : } slide_ctx;
1916 :
1917 0 : static void slide_init(slide_ctx *ctx, const u8 scalar[32])
1918 : {
1919 : // scalar is guaranteed to be below L, either because we checked (s),
1920 : // or because we reduced it modulo L (h_ram). L is under 2^253, so
1921 : // so bits 253 to 255 are guaranteed to be zero. No need to test them.
1922 : //
1923 : // Note however that L is very close to 2^252, so bit 252 is almost
1924 : // always zero. If we were to start at bit 251, the tests wouldn't
1925 : // catch the off-by-one error (constructing one that does would be
1926 : // prohibitively expensive).
1927 : //
1928 : // We should still check bit 252, though.
1929 0 : int i = 252;
1930 0 : while (i > 0 && scalar_bit(scalar, i) == 0) {
1931 0 : i--;
1932 : }
1933 0 : ctx->next_check = (u8)(i + 1);
1934 0 : ctx->next_index = -1;
1935 0 : ctx->next_digit = -1;
1936 0 : }
1937 :
1938 0 : static int slide_step(slide_ctx *ctx, int width, int i, const u8 scalar[32])
1939 : {
1940 0 : if (i == ctx->next_check) {
1941 0 : if (scalar_bit(scalar, i) == scalar_bit(scalar, i - 1)) {
1942 0 : ctx->next_check--;
1943 : } else {
1944 : // compute digit of next window
1945 0 : int w = MIN(width, i + 1);
1946 0 : int v = -(scalar_bit(scalar, i) << (w-1));
1947 0 : FOR_T (int, j, 0, w-1) {
1948 0 : v += scalar_bit(scalar, i-(w-1)+j) << j;
1949 : }
1950 0 : v += scalar_bit(scalar, i-w);
1951 0 : int lsb = v & (~v + 1); // smallest bit of v
1952 0 : int s = // log2(lsb)
1953 0 : (((lsb & 0xAA) != 0) << 0) |
1954 0 : (((lsb & 0xCC) != 0) << 1) |
1955 0 : (((lsb & 0xF0) != 0) << 2);
1956 0 : ctx->next_index = (i16)(i-(w-1)+s);
1957 0 : ctx->next_digit = (i8) (v >> s );
1958 0 : ctx->next_check -= (u8) w;
1959 : }
1960 : }
1961 0 : return i == ctx->next_index ? ctx->next_digit: 0;
1962 : }
1963 :
1964 : #define P_W_WIDTH 3 // Affects the size of the stack
1965 : #define B_W_WIDTH 5 // Affects the size of the binary
1966 : #define P_W_SIZE (1<<(P_W_WIDTH-2))
1967 :
1968 0 : int passgen_eddsa_check_equation(const u8 signature[64], const u8 public_key[32],
1969 : const u8 h[32])
1970 : {
1971 : ge minus_A; // -public_key
1972 : ge minus_R; // -first_half_of_signature
1973 0 : const u8 *s = signature + 32;
1974 :
1975 : // Check that A and R are on the curve
1976 : // Check that 0 <= S < L (prevents malleability)
1977 : // *Allow* non-cannonical encoding for A and R
1978 : {
1979 : u32 s32[8];
1980 0 : load32_le_buf(s32, s, 8);
1981 0 : if (ge_frombytes_neg_vartime(&minus_A, public_key) ||
1982 0 : ge_frombytes_neg_vartime(&minus_R, signature) ||
1983 0 : is_above_l(s32)) {
1984 0 : return -1;
1985 : }
1986 : }
1987 :
1988 : // look-up table for minus_A
1989 : ge_cached lutA[P_W_SIZE];
1990 : {
1991 : ge minus_A2, tmp;
1992 0 : ge_double(&minus_A2, &minus_A, &tmp);
1993 0 : ge_cache(&lutA[0], &minus_A);
1994 0 : FOR (i, 1, P_W_SIZE) {
1995 0 : ge_add(&tmp, &minus_A2, &lutA[i-1]);
1996 0 : ge_cache(&lutA[i], &tmp);
1997 : }
1998 : }
1999 :
2000 : // sum = [s]B - [h]A
2001 : // Merged double and add ladder, fused with sliding
2002 0 : slide_ctx h_slide; slide_init(&h_slide, h);
2003 0 : slide_ctx s_slide; slide_init(&s_slide, s);
2004 0 : int i = MAX(h_slide.next_check, s_slide.next_check);
2005 0 : ge *sum = &minus_A; // reuse minus_A for the sum
2006 0 : ge_zero(sum);
2007 0 : while (i >= 0) {
2008 : ge tmp;
2009 0 : ge_double(sum, sum, &tmp);
2010 0 : int h_digit = slide_step(&h_slide, P_W_WIDTH, i, h);
2011 0 : int s_digit = slide_step(&s_slide, B_W_WIDTH, i, s);
2012 0 : if (h_digit > 0) { ge_add(sum, sum, &lutA[ h_digit / 2]); }
2013 0 : if (h_digit < 0) { ge_sub(sum, sum, &lutA[-h_digit / 2]); }
2014 : fe t1, t2;
2015 0 : if (s_digit > 0) { ge_madd(sum, sum, b_window + s_digit/2, t1, t2); }
2016 0 : if (s_digit < 0) { ge_msub(sum, sum, b_window + -s_digit/2, t1, t2); }
2017 0 : i--;
2018 : }
2019 :
2020 : // Compare [8](sum-R) and the zero point
2021 : // The multiplication by 8 eliminates any low-order component
2022 : // and ensures consistency with batched verification.
2023 : ge_cached cached;
2024 : u8 check[32];
2025 : static const u8 zero_point[32] = {1}; // Point of order 1
2026 0 : ge_cache(&cached, &minus_R);
2027 0 : ge_add(sum, sum, &cached);
2028 0 : ge_double(sum, sum, &minus_R); // reuse minus_R as temporary
2029 0 : ge_double(sum, sum, &minus_R); // reuse minus_R as temporary
2030 0 : ge_double(sum, sum, &minus_R); // reuse minus_R as temporary
2031 0 : ge_tobytes(check, sum);
2032 0 : return passgen_verify32(check, zero_point);
2033 : }
2034 :
2035 : // 5-bit signed comb in cached format (Niels coordinates, Z=1)
2036 : static const ge_precomp b_comb_low[8] = {
2037 : {{-6816601,-2324159,-22559413,124364,18015490,
2038 : 8373481,19993724,1979872,-18549925,9085059,},
2039 : {10306321,403248,14839893,9633706,8463310,
2040 : -8354981,-14305673,14668847,26301366,2818560,},
2041 : {-22701500,-3210264,-13831292,-2927732,-16326337,
2042 : -14016360,12940910,177905,12165515,-2397893,},},
2043 : {{-12282262,-7022066,9920413,-3064358,-32147467,
2044 : 2927790,22392436,-14852487,2719975,16402117,},
2045 : {-7236961,-4729776,2685954,-6525055,-24242706,
2046 : -15940211,-6238521,14082855,10047669,12228189,},
2047 : {-30495588,-12893761,-11161261,3539405,-11502464,
2048 : 16491580,-27286798,-15030530,-7272871,-15934455,},},
2049 : {{17650926,582297,-860412,-187745,-12072900,
2050 : -10683391,-20352381,15557840,-31072141,-5019061,},
2051 : {-6283632,-2259834,-4674247,-4598977,-4089240,
2052 : 12435688,-31278303,1060251,6256175,10480726,},
2053 : {-13871026,2026300,-21928428,-2741605,-2406664,
2054 : -8034988,7355518,15733500,-23379862,7489131,},},
2055 : {{6883359,695140,23196907,9644202,-33430614,
2056 : 11354760,-20134606,6388313,-8263585,-8491918,},
2057 : {-7716174,-13605463,-13646110,14757414,-19430591,
2058 : -14967316,10359532,-11059670,-21935259,12082603,},
2059 : {-11253345,-15943946,10046784,5414629,24840771,
2060 : 8086951,-6694742,9868723,15842692,-16224787,},},
2061 : {{9639399,11810955,-24007778,-9320054,3912937,
2062 : -9856959,996125,-8727907,-8919186,-14097242,},
2063 : {7248867,14468564,25228636,-8795035,14346339,
2064 : 8224790,6388427,-7181107,6468218,-8720783,},
2065 : {15513115,15439095,7342322,-10157390,18005294,
2066 : -7265713,2186239,4884640,10826567,7135781,},},
2067 : {{-14204238,5297536,-5862318,-6004934,28095835,
2068 : 4236101,-14203318,1958636,-16816875,3837147,},
2069 : {-5511166,-13176782,-29588215,12339465,15325758,
2070 : -15945770,-8813185,11075932,-19608050,-3776283,},
2071 : {11728032,9603156,-4637821,-5304487,-7827751,
2072 : 2724948,31236191,-16760175,-7268616,14799772,},},
2073 : {{-28842672,4840636,-12047946,-9101456,-1445464,
2074 : 381905,-30977094,-16523389,1290540,12798615,},
2075 : {27246947,-10320914,14792098,-14518944,5302070,
2076 : -8746152,-3403974,-4149637,-27061213,10749585,},
2077 : {25572375,-6270368,-15353037,16037944,1146292,
2078 : 32198,23487090,9585613,24714571,-1418265,},},
2079 : {{19844825,282124,-17583147,11004019,-32004269,
2080 : -2716035,6105106,-1711007,-21010044,14338445,},
2081 : {8027505,8191102,-18504907,-12335737,25173494,
2082 : -5923905,15446145,7483684,-30440441,10009108,},
2083 : {-14134701,-4174411,10246585,-14677495,33553567,
2084 : -14012935,23366126,15080531,-7969992,7663473,},},
2085 : };
2086 :
2087 : static const ge_precomp b_comb_high[8] = {
2088 : {{33055887,-4431773,-521787,6654165,951411,
2089 : -6266464,-5158124,6995613,-5397442,-6985227,},
2090 : {4014062,6967095,-11977872,3960002,8001989,
2091 : 5130302,-2154812,-1899602,-31954493,-16173976,},
2092 : {16271757,-9212948,23792794,731486,-25808309,
2093 : -3546396,6964344,-4767590,10976593,10050757,},},
2094 : {{2533007,-4288439,-24467768,-12387405,-13450051,
2095 : 14542280,12876301,13893535,15067764,8594792,},
2096 : {20073501,-11623621,3165391,-13119866,13188608,
2097 : -11540496,-10751437,-13482671,29588810,2197295,},
2098 : {-1084082,11831693,6031797,14062724,14748428,
2099 : -8159962,-20721760,11742548,31368706,13161200,},},
2100 : {{2050412,-6457589,15321215,5273360,25484180,
2101 : 124590,-18187548,-7097255,-6691621,-14604792,},
2102 : {9938196,2162889,-6158074,-1711248,4278932,
2103 : -2598531,-22865792,-7168500,-24323168,11746309,},
2104 : {-22691768,-14268164,5965485,9383325,20443693,
2105 : 5854192,28250679,-1381811,-10837134,13717818,},},
2106 : {{-8495530,16382250,9548884,-4971523,-4491811,
2107 : -3902147,6182256,-12832479,26628081,10395408,},
2108 : {27329048,-15853735,7715764,8717446,-9215518,
2109 : -14633480,28982250,-5668414,4227628,242148,},
2110 : {-13279943,-7986904,-7100016,8764468,-27276630,
2111 : 3096719,29678419,-9141299,3906709,11265498,},},
2112 : {{11918285,15686328,-17757323,-11217300,-27548967,
2113 : 4853165,-27168827,6807359,6871949,-1075745,},
2114 : {-29002610,13984323,-27111812,-2713442,28107359,
2115 : -13266203,6155126,15104658,3538727,-7513788,},
2116 : {14103158,11233913,-33165269,9279850,31014152,
2117 : 4335090,-1827936,4590951,13960841,12787712,},},
2118 : {{1469134,-16738009,33411928,13942824,8092558,
2119 : -8778224,-11165065,1437842,22521552,-2792954,},
2120 : {31352705,-4807352,-25327300,3962447,12541566,
2121 : -9399651,-27425693,7964818,-23829869,5541287,},
2122 : {-25732021,-6864887,23848984,3039395,-9147354,
2123 : 6022816,-27421653,10590137,25309915,-1584678,},},
2124 : {{-22951376,5048948,31139401,-190316,-19542447,
2125 : -626310,-17486305,-16511925,-18851313,-12985140,},
2126 : {-9684890,14681754,30487568,7717771,-10829709,
2127 : 9630497,30290549,-10531496,-27798994,-13812825,},
2128 : {5827835,16097107,-24501327,12094619,7413972,
2129 : 11447087,28057551,-1793987,-14056981,4359312,},},
2130 : {{26323183,2342588,-21887793,-1623758,-6062284,
2131 : 2107090,-28724907,9036464,-19618351,-13055189,},
2132 : {-29697200,14829398,-4596333,14220089,-30022969,
2133 : 2955645,12094100,-13693652,-5941445,7047569,},
2134 : {-3201977,14413268,-12058324,-16417589,-9035655,
2135 : -7224648,9258160,1399236,30397584,-5684634,},},
2136 : };
2137 :
2138 0 : static void lookup_add(ge *p, ge_precomp *tmp_c, fe tmp_a, fe tmp_b,
2139 : const ge_precomp comb[8], const u8 scalar[32], int i)
2140 : {
2141 0 : u8 teeth = (u8)((scalar_bit(scalar, i) ) +
2142 0 : (scalar_bit(scalar, i + 32) << 1) +
2143 0 : (scalar_bit(scalar, i + 64) << 2) +
2144 0 : (scalar_bit(scalar, i + 96) << 3));
2145 0 : u8 high = teeth >> 3;
2146 0 : u8 index = (teeth ^ (high - 1)) & 7;
2147 0 : FOR (j, 0, 8) {
2148 0 : i32 select = 1 & (((j ^ index) - 1) >> 8);
2149 0 : fe_ccopy(tmp_c->Yp, comb[j].Yp, select);
2150 0 : fe_ccopy(tmp_c->Ym, comb[j].Ym, select);
2151 0 : fe_ccopy(tmp_c->T2, comb[j].T2, select);
2152 : }
2153 0 : fe_neg(tmp_a, tmp_c->T2);
2154 0 : fe_cswap(tmp_c->T2, tmp_a , high ^ 1);
2155 0 : fe_cswap(tmp_c->Yp, tmp_c->Ym, high ^ 1);
2156 0 : ge_madd(p, p, tmp_c, tmp_a, tmp_b);
2157 0 : }
2158 :
2159 : // p = [scalar]B, where B is the base point
2160 0 : static void ge_scalarmult_base(ge *p, const u8 scalar[32])
2161 : {
2162 : // twin 4-bits signed combs, from Mike Hamburg's
2163 : // Fast and compact elliptic-curve cryptography (2012)
2164 : // 1 / 2 modulo L
2165 : static const u8 half_mod_L[32] = {
2166 : 247,233,122,46,141,49,9,44,107,206,123,81,239,124,111,10,
2167 : 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,8,
2168 : };
2169 : // (2^256 - 1) / 2 modulo L
2170 : static const u8 half_ones[32] = {
2171 : 142,74,204,70,186,24,118,107,184,231,190,57,250,173,119,99,
2172 : 255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,7,
2173 : };
2174 :
2175 : // All bits set form: 1 means 1, 0 means -1
2176 : u8 s_scalar[32];
2177 0 : passgen_eddsa_mul_add(s_scalar, scalar, half_mod_L, half_ones);
2178 :
2179 : // Double and add ladder
2180 : fe tmp_a, tmp_b; // temporaries for addition
2181 : ge_precomp tmp_c; // temporary for comb lookup
2182 : ge tmp_d; // temporary for doubling
2183 0 : fe_1(tmp_c.Yp);
2184 0 : fe_1(tmp_c.Ym);
2185 0 : fe_0(tmp_c.T2);
2186 :
2187 : // Save a double on the first iteration
2188 0 : ge_zero(p);
2189 0 : lookup_add(p, &tmp_c, tmp_a, tmp_b, b_comb_low , s_scalar, 31);
2190 0 : lookup_add(p, &tmp_c, tmp_a, tmp_b, b_comb_high, s_scalar, 31+128);
2191 : // Regular double & add for the rest
2192 0 : for (int i = 30; i >= 0; i--) {
2193 0 : ge_double(p, p, &tmp_d);
2194 0 : lookup_add(p, &tmp_c, tmp_a, tmp_b, b_comb_low , s_scalar, i);
2195 0 : lookup_add(p, &tmp_c, tmp_a, tmp_b, b_comb_high, s_scalar, i+128);
2196 : }
2197 : // Note: we could save one addition at the end if we assumed the
2198 : // scalar fit in 252 bits. Which it does in practice if it is
2199 : // selected at random. However, non-random, non-hashed scalars
2200 : // *can* overflow 252 bits in practice. Better account for that
2201 : // than leaving that kind of subtle corner case.
2202 :
2203 0 : WIPE_BUFFER(tmp_a); WIPE_CTX(&tmp_d);
2204 0 : WIPE_BUFFER(tmp_b); WIPE_CTX(&tmp_c);
2205 0 : WIPE_BUFFER(s_scalar);
2206 0 : }
2207 :
2208 0 : void passgen_eddsa_scalarbase(u8 point[32], const u8 scalar[32])
2209 : {
2210 : ge P;
2211 0 : ge_scalarmult_base(&P, scalar);
2212 0 : ge_tobytes(point, &P);
2213 0 : WIPE_CTX(&P);
2214 0 : }
2215 :
2216 0 : void passgen_eddsa_key_pair(u8 secret_key[64], u8 public_key[32], u8 seed[32])
2217 : {
2218 : // To allow overlaps, observable writes happen in this order:
2219 : // 1. seed
2220 : // 2. secret_key
2221 : // 3. public_key
2222 : u8 a[64];
2223 0 : COPY(a, seed, 32);
2224 0 : passgen_wipe(seed, 32);
2225 0 : COPY(secret_key, a, 32);
2226 0 : passgen_blake2b(a, 64, a, 32);
2227 0 : passgen_eddsa_trim_scalar(a, a);
2228 0 : passgen_eddsa_scalarbase(secret_key + 32, a);
2229 0 : COPY(public_key, secret_key + 32, 32);
2230 0 : WIPE_BUFFER(a);
2231 0 : }
2232 :
2233 0 : static void hash_reduce(u8 h[32],
2234 : const u8 *a, size_t a_size,
2235 : const u8 *b, size_t b_size,
2236 : const u8 *c, size_t c_size)
2237 : {
2238 : u8 hash[64];
2239 : passgen_blake2b_ctx ctx;
2240 0 : passgen_blake2b_init (&ctx, 64);
2241 0 : passgen_blake2b_update(&ctx, a, a_size);
2242 0 : passgen_blake2b_update(&ctx, b, b_size);
2243 0 : passgen_blake2b_update(&ctx, c, c_size);
2244 0 : passgen_blake2b_final (&ctx, hash);
2245 0 : passgen_eddsa_reduce(h, hash);
2246 0 : }
2247 :
2248 : // Digital signature of a message with from a secret key.
2249 : //
2250 : // The secret key comprises two parts:
2251 : // - The seed that generates the key (secret_key[ 0..31])
2252 : // - The public key (secret_key[32..63])
2253 : //
2254 : // The seed and the public key are bundled together to make sure users
2255 : // don't use mismatched seeds and public keys, which would instantly
2256 : // leak the secret scalar and allow forgeries (allowing this to happen
2257 : // has resulted in critical vulnerabilities in the wild).
2258 : //
2259 : // The seed is hashed to derive the secret scalar and a secret prefix.
2260 : // The sole purpose of the prefix is to generate a secret random nonce.
2261 : // The properties of that nonce must be as follows:
2262 : // - Unique: we need a different one for each message.
2263 : // - Secret: third parties must not be able to predict it.
2264 : // - Random: any detectable bias would break all security.
2265 : //
2266 : // There are two ways to achieve these properties. The obvious one is
2267 : // to simply generate a random number. Here that would be a parameter
2268 : // (Monocypher doesn't have an RNG). It works, but then users may reuse
2269 : // the nonce by accident, which _also_ leaks the secret scalar and
2270 : // allows forgeries. This has happened in the wild too.
2271 : //
2272 : // This is no good, so instead we generate that nonce deterministically
2273 : // by reducing modulo L a hash of the secret prefix and the message.
2274 : // The secret prefix makes the nonce unpredictable, the message makes it
2275 : // unique, and the hash/reduce removes all bias.
2276 : //
2277 : // The cost of that safety is hashing the message twice. If that cost
2278 : // is unacceptable, there are two alternatives:
2279 : //
2280 : // - Signing a hash of the message instead of the message itself. This
2281 : // is fine as long as the hash is collision resistant. It is not
2282 : // compatible with existing "pure" signatures, but at least it's safe.
2283 : //
2284 : // - Using a random nonce. Please exercise **EXTREME CAUTION** if you
2285 : // ever do that. It is absolutely **critical** that the nonce is
2286 : // really an unbiased random number between 0 and L-1, never reused,
2287 : // and wiped immediately.
2288 : //
2289 : // To lower the likelihood of complete catastrophe if the RNG is
2290 : // either flawed or misused, you can hash the RNG output together with
2291 : // the secret prefix and the beginning of the message, and use the
2292 : // reduction of that hash instead of the RNG output itself. It's not
2293 : // foolproof (you'd need to hash the whole message) but it helps.
2294 : //
2295 : // Signing a message involves the following operations:
2296 : //
2297 : // scalar, prefix = HASH(secret_key)
2298 : // r = HASH(prefix || message) % L
2299 : // R = [r]B
2300 : // h = HASH(R || public_key || message) % L
2301 : // S = ((h * a) + r) % L
2302 : // signature = R || S
2303 0 : void passgen_eddsa_sign(u8 signature [64], const u8 secret_key[64],
2304 : const u8 *message, size_t message_size)
2305 : {
2306 : u8 a[64]; // secret scalar and prefix
2307 : u8 r[32]; // secret deterministic "random" nonce
2308 : u8 h[32]; // publically verifiable hash of the message (not wiped)
2309 : u8 R[32]; // first half of the signature (allows overlapping inputs)
2310 :
2311 0 : passgen_blake2b(a, 64, secret_key, 32);
2312 0 : passgen_eddsa_trim_scalar(a, a);
2313 0 : hash_reduce(r, a + 32, 32, message, message_size, 0, 0);
2314 0 : passgen_eddsa_scalarbase(R, r);
2315 0 : hash_reduce(h, R, 32, secret_key + 32, 32, message, message_size);
2316 0 : COPY(signature, R, 32);
2317 0 : passgen_eddsa_mul_add(signature + 32, h, a, r);
2318 :
2319 0 : WIPE_BUFFER(a);
2320 0 : WIPE_BUFFER(r);
2321 0 : }
2322 :
2323 : // To check the signature R, S of the message M with the public key A,
2324 : // there are 3 steps:
2325 : //
2326 : // compute h = HASH(R || A || message) % L
2327 : // check that A is on the curve.
2328 : // check that R == [s]B - [h]A
2329 : //
2330 : // The last two steps are done in passgen_eddsa_check_equation()
2331 0 : int passgen_eddsa_check(const u8 signature[64], const u8 public_key[32],
2332 : const u8 *message, size_t message_size)
2333 : {
2334 : u8 h[32];
2335 0 : hash_reduce(h, signature, 32, public_key, 32, message, message_size);
2336 0 : return passgen_eddsa_check_equation(signature, public_key, h);
2337 : }
2338 :
2339 : /////////////////////////
2340 : /// EdDSA <--> X25519 ///
2341 : /////////////////////////
2342 0 : void passgen_eddsa_to_x25519(u8 x25519[32], const u8 eddsa[32])
2343 : {
2344 : // (u, v) = ((1+y)/(1-y), sqrt(-486664)*u/x)
2345 : // Only converting y to u, the sign of x is ignored.
2346 : fe t1, t2;
2347 0 : fe_frombytes(t2, eddsa);
2348 0 : fe_add(t1, fe_one, t2);
2349 0 : fe_sub(t2, fe_one, t2);
2350 0 : fe_invert(t2, t2);
2351 0 : fe_mul(t1, t1, t2);
2352 0 : fe_tobytes(x25519, t1);
2353 0 : WIPE_BUFFER(t1);
2354 0 : WIPE_BUFFER(t2);
2355 0 : }
2356 :
2357 0 : void passgen_x25519_to_eddsa(u8 eddsa[32], const u8 x25519[32])
2358 : {
2359 : // (x, y) = (sqrt(-486664)*u/v, (u-1)/(u+1))
2360 : // Only converting u to y, x is assumed positive.
2361 : fe t1, t2;
2362 0 : fe_frombytes(t2, x25519);
2363 0 : fe_sub(t1, t2, fe_one);
2364 0 : fe_add(t2, t2, fe_one);
2365 0 : fe_invert(t2, t2);
2366 0 : fe_mul(t1, t1, t2);
2367 0 : fe_tobytes(eddsa, t1);
2368 0 : WIPE_BUFFER(t1);
2369 0 : WIPE_BUFFER(t2);
2370 0 : }
2371 :
2372 : /////////////////////////////////////////////
2373 : /// Dirty ephemeral public key generation ///
2374 : /////////////////////////////////////////////
2375 :
2376 : // Those functions generates a public key, *without* clearing the
2377 : // cofactor. Sending that key over the network leaks 3 bits of the
2378 : // private key. Use only to generate ephemeral keys that will be hidden
2379 : // with passgen_curve_to_hidden().
2380 : //
2381 : // The public key is otherwise compatible with passgen_x25519(), which
2382 : // properly clears the cofactor.
2383 : //
2384 : // Note that the distribution of the resulting public keys is almost
2385 : // uniform. Flipping the sign of the v coordinate (not provided by this
2386 : // function), covers the entire key space almost perfectly, where
2387 : // "almost" means a 2^-128 bias (undetectable). This uniformity is
2388 : // needed to ensure the proper randomness of the resulting
2389 : // representatives (once we apply passgen_curve_to_hidden()).
2390 : //
2391 : // Recall that Curve25519 has order C = 2^255 + e, with e < 2^128 (not
2392 : // to be confused with the prime order of the main subgroup, L, which is
2393 : // 8 times less than that).
2394 : //
2395 : // Generating all points would require us to multiply a point of order C
2396 : // (the base point plus any point of order 8) by all scalars from 0 to
2397 : // C-1. Clamping limits us to scalars between 2^254 and 2^255 - 1. But
2398 : // by negating the resulting point at random, we also cover scalars from
2399 : // -2^255 + 1 to -2^254 (which modulo C is congruent to e+1 to 2^254 + e).
2400 : //
2401 : // In practice:
2402 : // - Scalars from 0 to e + 1 are never generated
2403 : // - Scalars from 2^255 to 2^255 + e are never generated
2404 : // - Scalars from 2^254 + 1 to 2^254 + e are generated twice
2405 : //
2406 : // Since e < 2^128, detecting this bias requires observing over 2^100
2407 : // representatives from a given source (this will never happen), *and*
2408 : // recovering enough of the private key to determine that they do, or do
2409 : // not, belong to the biased set (this practically requires solving
2410 : // discrete logarithm, which is conjecturally intractable).
2411 : //
2412 : // In practice, this means the bias is impossible to detect.
2413 :
2414 : // s + (x*L) % 8*L
2415 : // Guaranteed to fit in 256 bits iff s fits in 255 bits.
2416 : // L < 2^253
2417 : // x%8 < 2^3
2418 : // L * (x%8) < 2^255
2419 : // s < 2^255
2420 : // s + L * (x%8) < 2^256
2421 0 : static void add_xl(u8 s[32], u8 x)
2422 : {
2423 0 : u64 mod8 = x & 7;
2424 0 : u64 carry = 0;
2425 0 : FOR (i , 0, 8) {
2426 0 : carry = carry + load32_le(s + 4*i) + L[i] * mod8;
2427 0 : store32_le(s + 4*i, (u32)carry);
2428 0 : carry >>= 32;
2429 : }
2430 0 : }
2431 :
2432 : // "Small" dirty ephemeral key.
2433 : // Use if you need to shrink the size of the binary, and can afford to
2434 : // slow down by a factor of two (compared to the fast version)
2435 : //
2436 : // This version works by decoupling the cofactor from the main factor.
2437 : //
2438 : // - The trimmed scalar determines the main factor
2439 : // - The clamped bits of the scalar determine the cofactor.
2440 : //
2441 : // Cofactor and main factor are combined into a single scalar, which is
2442 : // then multiplied by a point of order 8*L (unlike the base point, which
2443 : // has prime order). That "dirty" base point is the addition of the
2444 : // regular base point (9), and a point of order 8.
2445 0 : void passgen_x25519_dirty_small(u8 public_key[32], const u8 secret_key[32])
2446 : {
2447 : // Base point of order 8*L
2448 : // Raw scalar multiplication with it does not clear the cofactor,
2449 : // and the resulting public key will reveal 3 bits of the scalar.
2450 : //
2451 : // The low order component of this base point has been chosen
2452 : // to yield the same results as passgen_x25519_dirty_fast().
2453 : static const u8 dirty_base_point[32] = {
2454 : 0xd8, 0x86, 0x1a, 0xa2, 0x78, 0x7a, 0xd9, 0x26,
2455 : 0x8b, 0x74, 0x74, 0xb6, 0x82, 0xe3, 0xbe, 0xc3,
2456 : 0xce, 0x36, 0x9a, 0x1e, 0x5e, 0x31, 0x47, 0xa2,
2457 : 0x6d, 0x37, 0x7c, 0xfd, 0x20, 0xb5, 0xdf, 0x75,
2458 : };
2459 : // separate the main factor & the cofactor of the scalar
2460 : u8 scalar[32];
2461 0 : passgen_eddsa_trim_scalar(scalar, secret_key);
2462 :
2463 : // Separate the main factor and the cofactor
2464 : //
2465 : // The scalar is trimmed, so its cofactor is cleared. The three
2466 : // least significant bits however still have a main factor. We must
2467 : // remove it for X25519 compatibility.
2468 : //
2469 : // cofactor = lsb * L (modulo 8*L)
2470 : // combined = scalar + cofactor (modulo 8*L)
2471 0 : add_xl(scalar, secret_key[0]);
2472 0 : scalarmult(public_key, scalar, dirty_base_point, 256);
2473 0 : WIPE_BUFFER(scalar);
2474 0 : }
2475 :
2476 : // Select low order point
2477 : // We're computing the [cofactor]lop scalar multiplication, where:
2478 : //
2479 : // cofactor = tweak & 7.
2480 : // lop = (lop_x, lop_y)
2481 : // lop_x = sqrt((sqrt(d + 1) + 1) / d)
2482 : // lop_y = -lop_x * sqrtm1
2483 : //
2484 : // The low order point has order 8. There are 4 such points. We've
2485 : // chosen the one whose both coordinates are positive (below p/2).
2486 : // The 8 low order points are as follows:
2487 : //
2488 : // [0]lop = ( 0 , 1 )
2489 : // [1]lop = ( lop_x , lop_y)
2490 : // [2]lop = ( sqrt(-1), -0 )
2491 : // [3]lop = ( lop_x , -lop_y)
2492 : // [4]lop = (-0 , -1 )
2493 : // [5]lop = (-lop_x , -lop_y)
2494 : // [6]lop = (-sqrt(-1), 0 )
2495 : // [7]lop = (-lop_x , lop_y)
2496 : //
2497 : // The x coordinate is either 0, sqrt(-1), lop_x, or their opposite.
2498 : // The y coordinate is either 0, -1 , lop_y, or their opposite.
2499 : // The pattern for both is the same, except for a rotation of 2 (modulo 8)
2500 : //
2501 : // This helper function captures the pattern, and we can use it thus:
2502 : //
2503 : // select_lop(x, lop_x, sqrtm1, cofactor);
2504 : // select_lop(y, lop_y, fe_one, cofactor + 2);
2505 : //
2506 : // This is faster than an actual scalar multiplication,
2507 : // and requires less code than naive constant time look up.
2508 0 : static void select_lop(fe out, const fe x, const fe k, u8 cofactor)
2509 : {
2510 : fe tmp;
2511 0 : fe_0(out);
2512 0 : fe_ccopy(out, k , (cofactor >> 1) & 1); // bit 1
2513 0 : fe_ccopy(out, x , (cofactor >> 0) & 1); // bit 0
2514 0 : fe_neg (tmp, out);
2515 0 : fe_ccopy(out, tmp, (cofactor >> 2) & 1); // bit 2
2516 0 : WIPE_BUFFER(tmp);
2517 0 : }
2518 :
2519 : // "Fast" dirty ephemeral key
2520 : // We use this one by default.
2521 : //
2522 : // This version works by performing a regular scalar multiplication,
2523 : // then add a low order point. The scalar multiplication is done in
2524 : // Edwards space for more speed (*2 compared to the "small" version).
2525 : // The cost is a bigger binary for programs that don't also sign messages.
2526 0 : void passgen_x25519_dirty_fast(u8 public_key[32], const u8 secret_key[32])
2527 : {
2528 : // Compute clean scalar multiplication
2529 : u8 scalar[32];
2530 : ge pk;
2531 0 : passgen_eddsa_trim_scalar(scalar, secret_key);
2532 0 : ge_scalarmult_base(&pk, scalar);
2533 :
2534 : // Compute low order point
2535 : fe t1, t2;
2536 0 : select_lop(t1, lop_x, sqrtm1, secret_key[0]);
2537 0 : select_lop(t2, lop_y, fe_one, secret_key[0] + 2);
2538 : ge_precomp low_order_point;
2539 0 : fe_add(low_order_point.Yp, t2, t1);
2540 0 : fe_sub(low_order_point.Ym, t2, t1);
2541 0 : fe_mul(low_order_point.T2, t2, t1);
2542 0 : fe_mul(low_order_point.T2, low_order_point.T2, D2);
2543 :
2544 : // Add low order point to the public key
2545 0 : ge_madd(&pk, &pk, &low_order_point, t1, t2);
2546 :
2547 : // Convert to Montgomery u coordinate (we ignore the sign)
2548 0 : fe_add(t1, pk.Z, pk.Y);
2549 0 : fe_sub(t2, pk.Z, pk.Y);
2550 0 : fe_invert(t2, t2);
2551 0 : fe_mul(t1, t1, t2);
2552 :
2553 0 : fe_tobytes(public_key, t1);
2554 :
2555 0 : WIPE_BUFFER(t1); WIPE_CTX(&pk);
2556 0 : WIPE_BUFFER(t2); WIPE_CTX(&low_order_point);
2557 0 : WIPE_BUFFER(scalar);
2558 0 : }
2559 :
2560 : ///////////////////
2561 : /// Elligator 2 ///
2562 : ///////////////////
2563 : static const fe A = {486662};
2564 :
2565 : // Elligator direct map
2566 : //
2567 : // Computes the point corresponding to a representative, encoded in 32
2568 : // bytes (little Endian). Since positive representatives fits in 254
2569 : // bits, The two most significant bits are ignored.
2570 : //
2571 : // From the paper:
2572 : // w = -A / (fe(1) + non_square * r^2)
2573 : // e = chi(w^3 + A*w^2 + w)
2574 : // u = e*w - (fe(1)-e)*(A//2)
2575 : // v = -e * sqrt(u^3 + A*u^2 + u)
2576 : //
2577 : // We ignore v because we don't need it for X25519 (the Montgomery
2578 : // ladder only uses u).
2579 : //
2580 : // Note that e is either 0, 1 or -1
2581 : // if e = 0 u = 0 and v = 0
2582 : // if e = 1 u = w
2583 : // if e = -1 u = -w - A = w * non_square * r^2
2584 : //
2585 : // Let r1 = non_square * r^2
2586 : // Let r2 = 1 + r1
2587 : // Note that r2 cannot be zero, -1/non_square is not a square.
2588 : // We can (tediously) verify that:
2589 : // w^3 + A*w^2 + w = (A^2*r1 - r2^2) * A / r2^3
2590 : // Therefore:
2591 : // chi(w^3 + A*w^2 + w) = chi((A^2*r1 - r2^2) * (A / r2^3))
2592 : // chi(w^3 + A*w^2 + w) = chi((A^2*r1 - r2^2) * (A / r2^3)) * 1
2593 : // chi(w^3 + A*w^2 + w) = chi((A^2*r1 - r2^2) * (A / r2^3)) * chi(r2^6)
2594 : // chi(w^3 + A*w^2 + w) = chi((A^2*r1 - r2^2) * (A / r2^3) * r2^6)
2595 : // chi(w^3 + A*w^2 + w) = chi((A^2*r1 - r2^2) * A * r2^3)
2596 : // Corollary:
2597 : // e = 1 if (A^2*r1 - r2^2) * A * r2^3) is a non-zero square
2598 : // e = -1 if (A^2*r1 - r2^2) * A * r2^3) is not a square
2599 : // Note that w^3 + A*w^2 + w (and therefore e) can never be zero:
2600 : // w^3 + A*w^2 + w = w * (w^2 + A*w + 1)
2601 : // w^3 + A*w^2 + w = w * (w^2 + A*w + A^2/4 - A^2/4 + 1)
2602 : // w^3 + A*w^2 + w = w * (w + A/2)^2 - A^2/4 + 1)
2603 : // which is zero only if:
2604 : // w = 0 (impossible)
2605 : // (w + A/2)^2 = A^2/4 - 1 (impossible, because A^2/4-1 is not a square)
2606 : //
2607 : // Let isr = invsqrt((A^2*r1 - r2^2) * A * r2^3)
2608 : // isr = sqrt(1 / ((A^2*r1 - r2^2) * A * r2^3)) if e = 1
2609 : // isr = sqrt(sqrt(-1) / ((A^2*r1 - r2^2) * A * r2^3)) if e = -1
2610 : //
2611 : // if e = 1
2612 : // let u1 = -A * (A^2*r1 - r2^2) * A * r2^2 * isr^2
2613 : // u1 = w
2614 : // u1 = u
2615 : //
2616 : // if e = -1
2617 : // let ufactor = -non_square * sqrt(-1) * r^2
2618 : // let vfactor = sqrt(ufactor)
2619 : // let u2 = -A * (A^2*r1 - r2^2) * A * r2^2 * isr^2 * ufactor
2620 : // u2 = w * -1 * -non_square * r^2
2621 : // u2 = w * non_square * r^2
2622 : // u2 = u
2623 0 : void passgen_elligator_map(u8 curve[32], const u8 hidden[32])
2624 : {
2625 : fe r, u, t1, t2, t3;
2626 0 : fe_frombytes_mask(r, hidden, 2); // r is encoded in 254 bits.
2627 0 : fe_sq(r, r);
2628 0 : fe_add(t1, r, r);
2629 0 : fe_add(u, t1, fe_one);
2630 0 : fe_sq (t2, u);
2631 0 : fe_mul(t3, A2, t1);
2632 0 : fe_sub(t3, t3, t2);
2633 0 : fe_mul(t3, t3, A);
2634 0 : fe_mul(t1, t2, u);
2635 0 : fe_mul(t1, t3, t1);
2636 0 : int is_square = invsqrt(t1, t1);
2637 0 : fe_mul(u, r, ufactor);
2638 0 : fe_ccopy(u, fe_one, is_square);
2639 0 : fe_sq (t1, t1);
2640 0 : fe_mul(u, u, A);
2641 0 : fe_mul(u, u, t3);
2642 0 : fe_mul(u, u, t2);
2643 0 : fe_mul(u, u, t1);
2644 0 : fe_neg(u, u);
2645 0 : fe_tobytes(curve, u);
2646 :
2647 0 : WIPE_BUFFER(t1); WIPE_BUFFER(r);
2648 0 : WIPE_BUFFER(t2); WIPE_BUFFER(u);
2649 0 : WIPE_BUFFER(t3);
2650 0 : }
2651 :
2652 : // Elligator inverse map
2653 : //
2654 : // Computes the representative of a point, if possible. If not, it does
2655 : // nothing and returns -1. Note that the success of the operation
2656 : // depends only on the point (more precisely its u coordinate). The
2657 : // tweak parameter is used only upon success
2658 : //
2659 : // The tweak should be a random byte. Beyond that, its contents are an
2660 : // implementation detail. Currently, the tweak comprises:
2661 : // - Bit 1 : sign of the v coordinate (0 if positive, 1 if negative)
2662 : // - Bit 2-5: not used
2663 : // - Bits 6-7: random padding
2664 : //
2665 : // From the paper:
2666 : // Let sq = -non_square * u * (u+A)
2667 : // if sq is not a square, or u = -A, there is no mapping
2668 : // Assuming there is a mapping:
2669 : // if v is positive: r = sqrt(-u / (non_square * (u+A)))
2670 : // if v is negative: r = sqrt(-(u+A) / (non_square * u ))
2671 : //
2672 : // We compute isr = invsqrt(-non_square * u * (u+A))
2673 : // if it wasn't a square, abort.
2674 : // else, isr = sqrt(-1 / (non_square * u * (u+A))
2675 : //
2676 : // If v is positive, we return isr * u:
2677 : // isr * u = sqrt(-1 / (non_square * u * (u+A)) * u
2678 : // isr * u = sqrt(-u / (non_square * (u+A))
2679 : //
2680 : // If v is negative, we return isr * (u+A):
2681 : // isr * (u+A) = sqrt(-1 / (non_square * u * (u+A)) * (u+A)
2682 : // isr * (u+A) = sqrt(-(u+A) / (non_square * u)
2683 0 : int passgen_elligator_rev(u8 hidden[32], const u8 public_key[32], u8 tweak)
2684 : {
2685 : fe t1, t2, t3;
2686 0 : fe_frombytes(t1, public_key); // t1 = u
2687 :
2688 0 : fe_add(t2, t1, A); // t2 = u + A
2689 0 : fe_mul(t3, t1, t2);
2690 0 : fe_mul_small(t3, t3, -2);
2691 0 : int is_square = invsqrt(t3, t3); // t3 = sqrt(-1 / non_square * u * (u+A))
2692 0 : if (is_square) {
2693 : // The only variable time bit. This ultimately reveals how many
2694 : // tries it took us to find a representable key.
2695 : // This does not affect security as long as we try keys at random.
2696 :
2697 0 : fe_ccopy (t1, t2, tweak & 1); // multiply by u if v is positive,
2698 0 : fe_mul (t3, t1, t3); // multiply by u+A otherwise
2699 0 : fe_mul_small(t1, t3, 2);
2700 0 : fe_neg (t2, t3);
2701 0 : fe_ccopy (t3, t2, fe_isodd(t1));
2702 0 : fe_tobytes(hidden, t3);
2703 :
2704 : // Pad with two random bits
2705 0 : hidden[31] |= tweak & 0xc0;
2706 : }
2707 :
2708 0 : WIPE_BUFFER(t1);
2709 0 : WIPE_BUFFER(t2);
2710 0 : WIPE_BUFFER(t3);
2711 0 : return is_square - 1;
2712 : }
2713 :
2714 0 : void passgen_elligator_key_pair(u8 hidden[32], u8 secret_key[32], u8 seed[32])
2715 : {
2716 : u8 pk [32]; // public key
2717 : u8 buf[64]; // seed + representative
2718 0 : COPY(buf + 32, seed, 32);
2719 : do {
2720 0 : passgen_chacha20_djb(buf, 0, 64, buf+32, zero, 0);
2721 0 : passgen_x25519_dirty_fast(pk, buf); // or the "small" version
2722 0 : } while(passgen_elligator_rev(buf+32, pk, buf[32]));
2723 : // Note that the return value of passgen_elligator_rev() is
2724 : // independent from its tweak parameter.
2725 : // Therefore, buf[32] is not actually reused. Either we loop one
2726 : // more time and buf[32] is used for the new seed, or we succeeded,
2727 : // and buf[32] becomes the tweak parameter.
2728 :
2729 0 : passgen_wipe(seed, 32);
2730 0 : COPY(hidden , buf + 32, 32);
2731 0 : COPY(secret_key, buf , 32);
2732 0 : WIPE_BUFFER(buf);
2733 0 : WIPE_BUFFER(pk);
2734 0 : }
2735 :
2736 : ///////////////////////
2737 : /// Scalar division ///
2738 : ///////////////////////
2739 :
2740 : // Montgomery reduction.
2741 : // Divides x by (2^256), and reduces the result modulo L
2742 : //
2743 : // Precondition:
2744 : // x < L * 2^256
2745 : // Constants:
2746 : // r = 2^256 (makes division by r trivial)
2747 : // k = (r * (1/r) - 1) // L (1/r is computed modulo L )
2748 : // Algorithm:
2749 : // s = (x * k) % r
2750 : // t = x + s*L (t is always a multiple of r)
2751 : // u = (t/r) % L (u is always below 2*L, conditional subtraction is enough)
2752 0 : static void redc(u32 u[8], u32 x[16])
2753 : {
2754 : static const u32 k[8] = {
2755 : 0x12547e1b, 0xd2b51da3, 0xfdba84ff, 0xb1a206f2,
2756 : 0xffa36bea, 0x14e75438, 0x6fe91836, 0x9db6c6f2,
2757 : };
2758 :
2759 : // s = x * k (modulo 2^256)
2760 : // This is cheaper than the full multiplication.
2761 0 : u32 s[8] = {0};
2762 0 : FOR (i, 0, 8) {
2763 0 : u64 carry = 0;
2764 0 : FOR (j, 0, 8-i) {
2765 0 : carry += s[i+j] + (u64)x[i] * k[j];
2766 0 : s[i+j] = (u32)carry;
2767 0 : carry >>= 32;
2768 : }
2769 : }
2770 0 : u32 t[16] = {0};
2771 0 : multiply(t, s, L);
2772 :
2773 : // t = t + x
2774 0 : u64 carry = 0;
2775 0 : FOR (i, 0, 16) {
2776 0 : carry += (u64)t[i] + x[i];
2777 0 : t[i] = (u32)carry;
2778 0 : carry >>= 32;
2779 : }
2780 :
2781 : // u = (t / 2^256) % L
2782 : // Note that t / 2^256 is always below 2*L,
2783 : // So a constant time conditional subtraction is enough
2784 0 : remove_l(u, t+8);
2785 :
2786 0 : WIPE_BUFFER(s);
2787 0 : WIPE_BUFFER(t);
2788 0 : }
2789 :
2790 0 : void passgen_x25519_inverse(u8 blind_salt [32], const u8 private_key[32],
2791 : const u8 curve_point[32])
2792 : {
2793 : static const u8 Lm2[32] = { // L - 2
2794 : 0xeb, 0xd3, 0xf5, 0x5c, 0x1a, 0x63, 0x12, 0x58,
2795 : 0xd6, 0x9c, 0xf7, 0xa2, 0xde, 0xf9, 0xde, 0x14,
2796 : 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
2797 : 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10,
2798 : };
2799 : // 1 in Montgomery form
2800 0 : u32 m_inv [8] = {
2801 : 0x8d98951d, 0xd6ec3174, 0x737dcf70, 0xc6ef5bf4,
2802 : 0xfffffffe, 0xffffffff, 0xffffffff, 0x0fffffff,
2803 : };
2804 :
2805 : u8 scalar[32];
2806 0 : passgen_eddsa_trim_scalar(scalar, private_key);
2807 :
2808 : // Convert the scalar in Montgomery form
2809 : // m_scl = scalar * 2^256 (modulo L)
2810 : u32 m_scl[8];
2811 : {
2812 : u32 tmp[16];
2813 0 : ZERO(tmp, 8);
2814 0 : load32_le_buf(tmp+8, scalar, 8);
2815 0 : mod_l(scalar, tmp);
2816 0 : load32_le_buf(m_scl, scalar, 8);
2817 0 : WIPE_BUFFER(tmp); // Wipe ASAP to save stack space
2818 : }
2819 :
2820 : // Compute the inverse
2821 : u32 product[16];
2822 0 : for (int i = 252; i >= 0; i--) {
2823 0 : ZERO(product, 16);
2824 0 : multiply(product, m_inv, m_inv);
2825 0 : redc(m_inv, product);
2826 0 : if (scalar_bit(Lm2, i)) {
2827 0 : ZERO(product, 16);
2828 0 : multiply(product, m_inv, m_scl);
2829 0 : redc(m_inv, product);
2830 : }
2831 : }
2832 : // Convert the inverse *out* of Montgomery form
2833 : // scalar = m_inv / 2^256 (modulo L)
2834 0 : COPY(product, m_inv, 8);
2835 0 : ZERO(product + 8, 8);
2836 0 : redc(m_inv, product);
2837 0 : store32_le_buf(scalar, m_inv, 8); // the *inverse* of the scalar
2838 :
2839 : // Clear the cofactor of scalar:
2840 : // cleared = scalar * (3*L + 1) (modulo 8*L)
2841 : // cleared = scalar + scalar * 3 * L (modulo 8*L)
2842 : // Note that (scalar * 3) is reduced modulo 8, so we only need the
2843 : // first byte.
2844 0 : add_xl(scalar, scalar[0] * 3);
2845 :
2846 : // Recall that 8*L < 2^256. However it is also very close to
2847 : // 2^255. If we spanned the ladder over 255 bits, random tests
2848 : // wouldn't catch the off-by-one error.
2849 0 : scalarmult(blind_salt, scalar, curve_point, 256);
2850 :
2851 0 : WIPE_BUFFER(scalar); WIPE_BUFFER(m_scl);
2852 0 : WIPE_BUFFER(product); WIPE_BUFFER(m_inv);
2853 0 : }
2854 :
2855 : ////////////////////////////////
2856 : /// Authenticated encryption ///
2857 : ////////////////////////////////
2858 0 : static void lock_auth(u8 mac[16], const u8 auth_key[32],
2859 : const u8 *ad , size_t ad_size,
2860 : const u8 *cipher_text, size_t text_size)
2861 : {
2862 : u8 sizes[16]; // Not secret, not wiped
2863 0 : store64_le(sizes + 0, ad_size);
2864 0 : store64_le(sizes + 8, text_size);
2865 : passgen_poly1305_ctx poly_ctx; // auto wiped...
2866 0 : passgen_poly1305_init (&poly_ctx, auth_key);
2867 0 : passgen_poly1305_update(&poly_ctx, ad , ad_size);
2868 0 : passgen_poly1305_update(&poly_ctx, zero , gap(ad_size, 16));
2869 0 : passgen_poly1305_update(&poly_ctx, cipher_text, text_size);
2870 0 : passgen_poly1305_update(&poly_ctx, zero , gap(text_size, 16));
2871 0 : passgen_poly1305_update(&poly_ctx, sizes , 16);
2872 0 : passgen_poly1305_final (&poly_ctx, mac); // ...here
2873 0 : }
2874 :
2875 0 : void passgen_aead_init_x(passgen_aead_ctx *ctx,
2876 : u8 const key[32], const u8 nonce[24])
2877 : {
2878 0 : passgen_chacha20_h(ctx->key, key, nonce);
2879 0 : COPY(ctx->nonce, nonce + 16, 8);
2880 0 : ctx->counter = 0;
2881 0 : }
2882 :
2883 0 : void passgen_aead_init_djb(passgen_aead_ctx *ctx,
2884 : const u8 key[32], const u8 nonce[8])
2885 : {
2886 0 : COPY(ctx->key , key , 32);
2887 0 : COPY(ctx->nonce, nonce, 8);
2888 0 : ctx->counter = 0;
2889 0 : }
2890 :
2891 0 : void passgen_aead_init_ietf(passgen_aead_ctx *ctx,
2892 : const u8 key[32], const u8 nonce[12])
2893 : {
2894 0 : COPY(ctx->key , key , 32);
2895 0 : COPY(ctx->nonce, nonce + 4, 8);
2896 0 : ctx->counter = (u64)load32_le(nonce) << 32;
2897 0 : }
2898 :
2899 0 : void passgen_aead_write(passgen_aead_ctx *ctx, u8 *cipher_text, u8 mac[16],
2900 : const u8 *ad, size_t ad_size,
2901 : const u8 *plain_text, size_t text_size)
2902 : {
2903 : u8 auth_key[64]; // the last 32 bytes are used for rekeying.
2904 0 : passgen_chacha20_djb(auth_key, 0, 64, ctx->key, ctx->nonce, ctx->counter);
2905 0 : passgen_chacha20_djb(cipher_text, plain_text, text_size,
2906 0 : ctx->key, ctx->nonce, ctx->counter + 1);
2907 0 : lock_auth(mac, auth_key, ad, ad_size, cipher_text, text_size);
2908 0 : COPY(ctx->key, auth_key + 32, 32);
2909 0 : WIPE_BUFFER(auth_key);
2910 0 : }
2911 :
2912 0 : int passgen_aead_read(passgen_aead_ctx *ctx, u8 *plain_text, const u8 mac[16],
2913 : const u8 *ad, size_t ad_size,
2914 : const u8 *cipher_text, size_t text_size)
2915 : {
2916 : u8 auth_key[64]; // the last 32 bytes are used for rekeying.
2917 : u8 real_mac[16];
2918 0 : passgen_chacha20_djb(auth_key, 0, 64, ctx->key, ctx->nonce, ctx->counter);
2919 0 : lock_auth(real_mac, auth_key, ad, ad_size, cipher_text, text_size);
2920 0 : int mismatch = passgen_verify16(mac, real_mac);
2921 0 : if (!mismatch) {
2922 0 : passgen_chacha20_djb(plain_text, cipher_text, text_size,
2923 0 : ctx->key, ctx->nonce, ctx->counter + 1);
2924 0 : COPY(ctx->key, auth_key + 32, 32);
2925 : }
2926 0 : WIPE_BUFFER(auth_key);
2927 0 : WIPE_BUFFER(real_mac);
2928 0 : return mismatch;
2929 : }
2930 :
2931 0 : void passgen_aead_lock(u8 *cipher_text, u8 mac[16], const u8 key[32],
2932 : const u8 nonce[24], const u8 *ad, size_t ad_size,
2933 : const u8 *plain_text, size_t text_size)
2934 : {
2935 : passgen_aead_ctx ctx;
2936 0 : passgen_aead_init_x(&ctx, key, nonce);
2937 0 : passgen_aead_write(&ctx, cipher_text, mac, ad, ad_size,
2938 : plain_text, text_size);
2939 0 : passgen_wipe(&ctx, sizeof(ctx));
2940 0 : }
2941 :
2942 0 : int passgen_aead_unlock(u8 *plain_text, const u8 mac[16], const u8 key[32],
2943 : const u8 nonce[24], const u8 *ad, size_t ad_size,
2944 : const u8 *cipher_text, size_t text_size)
2945 : {
2946 : passgen_aead_ctx ctx;
2947 0 : passgen_aead_init_x(&ctx, key, nonce);
2948 0 : int mismatch = passgen_aead_read(&ctx, plain_text, mac, ad, ad_size,
2949 : cipher_text, text_size);
2950 0 : passgen_wipe(&ctx, sizeof(ctx));
2951 0 : return mismatch;
2952 : }
2953 :
2954 : #ifdef MONOCYPHER_CPP_NAMESPACE
2955 : }
2956 : #endif
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