1 /* crypto/bn/bn_mont.c */
2 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
5 * This package is an SSL implementation written
6 * by Eric Young (eay@cryptsoft.com).
7 * The implementation was written so as to conform with Netscapes SSL.
9 * This library is free for commercial and non-commercial use as long as
10 * the following conditions are aheared to. The following conditions
11 * apply to all code found in this distribution, be it the RC4, RSA,
12 * lhash, DES, etc., code; not just the SSL code. The SSL documentation
13 * included with this distribution is covered by the same copyright terms
14 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
16 * Copyright remains Eric Young's, and as such any Copyright notices in
17 * the code are not to be removed.
18 * If this package is used in a product, Eric Young should be given attribution
19 * as the author of the parts of the library used.
20 * This can be in the form of a textual message at program startup or
21 * in documentation (online or textual) provided with the package.
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
26 * 1. Redistributions of source code must retain the copyright
27 * notice, this list of conditions and the following disclaimer.
28 * 2. Redistributions in binary form must reproduce the above copyright
29 * notice, this list of conditions and the following disclaimer in the
30 * documentation and/or other materials provided with the distribution.
31 * 3. All advertising materials mentioning features or use of this software
32 * must display the following acknowledgement:
33 * "This product includes cryptographic software written by
34 * Eric Young (eay@cryptsoft.com)"
35 * The word 'cryptographic' can be left out if the rouines from the library
36 * being used are not cryptographic related :-).
37 * 4. If you include any Windows specific code (or a derivative thereof) from
38 * the apps directory (application code) you must include an acknowledgement:
39 * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
41 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
42 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
43 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
44 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
45 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
46 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
47 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
48 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
49 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
50 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
53 * The licence and distribution terms for any publically available version or
54 * derivative of this code cannot be changed. i.e. this code cannot simply be
55 * copied and put under another distribution licence
56 * [including the GNU Public Licence.]
58 /* ====================================================================
59 * Copyright (c) 1998-2018 The OpenSSL Project. All rights reserved.
61 * Redistribution and use in source and binary forms, with or without
62 * modification, are permitted provided that the following conditions
65 * 1. Redistributions of source code must retain the above copyright
66 * notice, this list of conditions and the following disclaimer.
68 * 2. Redistributions in binary form must reproduce the above copyright
69 * notice, this list of conditions and the following disclaimer in
70 * the documentation and/or other materials provided with the
73 * 3. All advertising materials mentioning features or use of this
74 * software must display the following acknowledgment:
75 * "This product includes software developed by the OpenSSL Project
76 * for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
78 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
79 * endorse or promote products derived from this software without
80 * prior written permission. For written permission, please contact
81 * openssl-core@openssl.org.
83 * 5. Products derived from this software may not be called "OpenSSL"
84 * nor may "OpenSSL" appear in their names without prior written
85 * permission of the OpenSSL Project.
87 * 6. Redistributions of any form whatsoever must retain the following
89 * "This product includes software developed by the OpenSSL Project
90 * for use in the OpenSSL Toolkit (http://www.openssl.org/)"
92 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
93 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
94 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
95 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
96 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
97 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
98 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
99 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
100 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
101 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
102 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
103 * OF THE POSSIBILITY OF SUCH DAMAGE.
104 * ====================================================================
106 * This product includes cryptographic software written by Eric Young
107 * (eay@cryptsoft.com). This product includes software written by Tim
108 * Hudson (tjh@cryptsoft.com).
113 * Details about Montgomery multiplication algorithms can be found at
114 * http://security.ece.orst.edu/publications.html, e.g.
115 * http://security.ece.orst.edu/koc/papers/j37acmon.pdf and
116 * sections 3.8 and 4.2 in http://security.ece.orst.edu/koc/papers/r01rsasw.pdf
120 #include "cryptlib.h"
123 #define MONT_WORD /* use the faster word-based algorithm */
126 static int bn_from_montgomery_word(BIGNUM *ret, BIGNUM *r, BN_MONT_CTX *mont);
129 int BN_mod_mul_montgomery(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
130 BN_MONT_CTX *mont, BN_CTX *ctx)
132 int ret = bn_mul_mont_fixed_top(r, a, b, mont, ctx);
140 int bn_mul_mont_fixed_top(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
141 BN_MONT_CTX *mont, BN_CTX *ctx)
145 #if defined(OPENSSL_BN_ASM_MONT) && defined(MONT_WORD)
146 int num = mont->N.top;
148 if (num > 1 && a->top == num && b->top == num) {
149 if (bn_wexpand(r, num) == NULL)
151 if (bn_mul_mont(r->d, a->d, b->d, mont->N.d, mont->n0, num)) {
152 r->neg = a->neg ^ b->neg;
154 r->flags |= BN_FLG_FIXED_TOP;
161 tmp = BN_CTX_get(ctx);
167 if (!BN_sqr(tmp, a, ctx))
170 if (!BN_mul(tmp, a, b, ctx))
173 /* reduce from aRR to aR */
175 if (!bn_from_montgomery_word(r, tmp, mont))
178 if (!BN_from_montgomery(r, tmp, mont, ctx))
188 static int bn_from_montgomery_word(BIGNUM *ret, BIGNUM *r, BN_MONT_CTX *mont)
191 BN_ULONG *ap, *np, *rp, n0, v, carry;
201 max = (2 * nl); /* carry is stored separately */
202 if (bn_wexpand(r, max) == NULL)
209 /* clear the top words of T */
211 for (i = r->top; i < max; i++) /* memset? XXX */
214 memset(&(rp[r->top]), 0, (max - r->top) * sizeof(BN_ULONG));
218 r->flags |= BN_FLG_FIXED_TOP;
222 * Add multiples of |n| to |r| until R = 2^(nl * BN_BITS2) divides it. On
223 * input, we had |r| < |n| * R, so now |r| < 2 * |n| * R. Note that |r|
224 * includes |carry| which is stored separately.
226 for (carry = 0, i = 0; i < nl; i++, rp++) {
227 v = bn_mul_add_words(rp, np, nl, (rp[0] * n0) & BN_MASK2);
228 v = (v + carry + rp[nl]) & BN_MASK2;
229 carry |= (v != rp[nl]);
230 carry &= (v <= rp[nl]);
234 if (bn_wexpand(ret, nl) == NULL)
237 ret->flags |= BN_FLG_FIXED_TOP;
243 * Shift |nl| words to divide by R. We have |ap| < 2 * |n|. Note that |ap|
244 * includes |carry| which is stored separately.
248 carry -= bn_sub_words(rp, ap, np, nl);
250 * |carry| is -1 if |ap| - |np| underflowed or zero if it did not. Note
251 * |carry| cannot be 1. That would imply the subtraction did not fit in
252 * |nl| words, and we know at most one subtraction is needed.
254 for (i = 0; i < nl; i++) {
255 rp[i] = (carry & ap[i]) | (~carry & rp[i]);
261 #endif /* MONT_WORD */
263 int BN_from_montgomery(BIGNUM *ret, const BIGNUM *a, BN_MONT_CTX *mont,
271 if ((t = BN_CTX_get(ctx)) && BN_copy(t, a)) {
272 retn = bn_from_montgomery_word(ret, t, mont);
277 #else /* !MONT_WORD */
281 t1 = BN_CTX_get(ctx);
282 t2 = BN_CTX_get(ctx);
283 if (t1 == NULL || t2 == NULL)
288 BN_mask_bits(t1, mont->ri);
290 if (!BN_mul(t2, t1, &mont->Ni, ctx))
292 BN_mask_bits(t2, mont->ri);
294 if (!BN_mul(t1, t2, &mont->N, ctx))
296 if (!BN_add(t2, a, t1))
298 if (!BN_rshift(ret, t2, mont->ri))
301 if (BN_ucmp(ret, &(mont->N)) >= 0) {
302 if (!BN_usub(ret, ret, &(mont->N)))
309 #endif /* MONT_WORD */
313 int bn_to_mont_fixed_top(BIGNUM *r, const BIGNUM *a, BN_MONT_CTX *mont,
316 return bn_mul_mont_fixed_top(r, a, &(mont->RR), mont, ctx);
319 BN_MONT_CTX *BN_MONT_CTX_new(void)
323 if ((ret = (BN_MONT_CTX *)OPENSSL_malloc(sizeof(BN_MONT_CTX))) == NULL)
326 BN_MONT_CTX_init(ret);
327 ret->flags = BN_FLG_MALLOCED;
331 void BN_MONT_CTX_init(BN_MONT_CTX *ctx)
337 ctx->n0[0] = ctx->n0[1] = 0;
341 void BN_MONT_CTX_free(BN_MONT_CTX *mont)
346 BN_clear_free(&(mont->RR));
347 BN_clear_free(&(mont->N));
348 BN_clear_free(&(mont->Ni));
349 if (mont->flags & BN_FLG_MALLOCED)
353 int BN_MONT_CTX_set(BN_MONT_CTX *mont, const BIGNUM *mod, BN_CTX *ctx)
362 if ((Ri = BN_CTX_get(ctx)) == NULL)
364 R = &(mont->RR); /* grab RR as a temp */
365 if (!BN_copy(&(mont->N), mod))
366 goto err; /* Set N */
367 if (BN_get_flags(mod, BN_FLG_CONSTTIME) != 0)
368 BN_set_flags(&(mont->N), BN_FLG_CONSTTIME);
381 if (BN_get_flags(mod, BN_FLG_CONSTTIME) != 0)
382 BN_set_flags(&tmod, BN_FLG_CONSTTIME);
384 mont->ri = (BN_num_bits(mod) + (BN_BITS2 - 1)) / BN_BITS2 * BN_BITS2;
386 # if defined(OPENSSL_BN_ASM_MONT) && (BN_BITS2<=32)
388 * Only certain BN_BITS2<=32 platforms actually make use of n0[1],
389 * and we could use the #else case (with a shorter R value) for the
390 * others. However, currently only the assembler files do know which
395 if (!(BN_set_bit(R, 2 * BN_BITS2)))
399 if ((buf[0] = mod->d[0]))
401 if ((buf[1] = mod->top > 1 ? mod->d[1] : 0))
404 if ((BN_mod_inverse(Ri, R, &tmod, ctx)) == NULL)
406 if (!BN_lshift(Ri, Ri, 2 * BN_BITS2))
408 if (!BN_is_zero(Ri)) {
409 if (!BN_sub_word(Ri, 1))
411 } else { /* if N mod word size == 1 */
413 if (bn_expand(Ri, (int)sizeof(BN_ULONG) * 2) == NULL)
415 /* Ri-- (mod double word size) */
421 if (!BN_div(Ri, NULL, Ri, &tmod, ctx))
424 * Ni = (R*Ri-1)/N, keep only couple of least significant words:
426 mont->n0[0] = (Ri->top > 0) ? Ri->d[0] : 0;
427 mont->n0[1] = (Ri->top > 1) ? Ri->d[1] : 0;
430 if (!(BN_set_bit(R, BN_BITS2)))
433 buf[0] = mod->d[0]; /* tmod = N mod word size */
435 tmod.top = buf[0] != 0 ? 1 : 0;
436 /* Ri = R^-1 mod N */
437 if ((BN_mod_inverse(Ri, R, &tmod, ctx)) == NULL)
439 if (!BN_lshift(Ri, Ri, BN_BITS2))
441 if (!BN_is_zero(Ri)) {
442 if (!BN_sub_word(Ri, 1))
444 } else { /* if N mod word size == 1 */
446 if (!BN_set_word(Ri, BN_MASK2))
447 goto err; /* Ri-- (mod word size) */
449 if (!BN_div(Ri, NULL, Ri, &tmod, ctx))
452 * Ni = (R*Ri-1)/N, keep only least significant word:
454 mont->n0[0] = (Ri->top > 0) ? Ri->d[0] : 0;
458 #else /* !MONT_WORD */
459 { /* bignum version */
460 mont->ri = BN_num_bits(&mont->N);
462 if (!BN_set_bit(R, mont->ri))
463 goto err; /* R = 2^ri */
464 /* Ri = R^-1 mod N */
465 if ((BN_mod_inverse(Ri, R, &mont->N, ctx)) == NULL)
467 if (!BN_lshift(Ri, Ri, mont->ri))
469 if (!BN_sub_word(Ri, 1))
474 if (!BN_div(&(mont->Ni), NULL, Ri, &mont->N, ctx))
479 /* setup RR for conversions */
480 BN_zero(&(mont->RR));
481 if (!BN_set_bit(&(mont->RR), mont->ri * 2))
483 if (!BN_mod(&(mont->RR), &(mont->RR), &(mont->N), ctx))
486 for (i = mont->RR.top, ret = mont->N.top; i < ret; i++)
489 mont->RR.flags |= BN_FLG_FIXED_TOP;
497 BN_MONT_CTX *BN_MONT_CTX_copy(BN_MONT_CTX *to, BN_MONT_CTX *from)
502 if (!BN_copy(&(to->RR), &(from->RR)))
504 if (!BN_copy(&(to->N), &(from->N)))
506 if (!BN_copy(&(to->Ni), &(from->Ni)))
509 to->n0[0] = from->n0[0];
510 to->n0[1] = from->n0[1];
514 BN_MONT_CTX *BN_MONT_CTX_set_locked(BN_MONT_CTX **pmont, int lock,
515 const BIGNUM *mod, BN_CTX *ctx)
521 CRYPTO_r_unlock(lock);
526 * We don't want to serialise globally while doing our lazy-init math in
527 * BN_MONT_CTX_set. That punishes threads that are doing independent
528 * things. Instead, punish the case where more than one thread tries to
529 * lazy-init the same 'pmont', by having each do the lazy-init math work
530 * independently and only use the one from the thread that wins the race
531 * (the losers throw away the work they've done).
533 ret = BN_MONT_CTX_new();
536 if (!BN_MONT_CTX_set(ret, mod, ctx)) {
537 BN_MONT_CTX_free(ret);
541 /* The locked compare-and-set, after the local work is done. */
544 BN_MONT_CTX_free(ret);
548 CRYPTO_w_unlock(lock);