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.]
60 * Details about Montgomery multiplication algorithms can be found at
61 * http://security.ece.orst.edu/publications.html, e.g.
62 * http://security.ece.orst.edu/koc/papers/j37acmon.pdf and
63 * sections 3.8 and 4.2 in http://security.ece.orst.edu/koc/papers/r01rsasw.pdf
70 #define MONT_WORD /* use the faster word-based algorithm */
72 int BN_mod_mul_montgomery(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
73 BN_MONT_CTX *mont, BN_CTX *ctx)
77 #ifdef OPENSSL_BN_ASM_MONT
78 int num = mont->N.top;
80 if (num>1 && a->top==num && b->top==num)
82 if (bn_wexpand(r,num) == NULL) return 0;
83 if (bn_mul_mont(r->d,a->d,b->d,mont->N.d,mont->n0,num))
85 r->neg = a->neg^b->neg;
94 tmp = BN_CTX_get(ctx);
95 if (tmp == NULL) goto err;
100 if (!BN_sqr(tmp,a,ctx)) goto err;
104 if (!BN_mul(tmp,a,b,ctx)) goto err;
106 /* reduce from aRR to aR */
107 if (!BN_from_montgomery(r,tmp,mont,ctx)) goto err;
115 int BN_from_montgomery(BIGNUM *ret, const BIGNUM *a, BN_MONT_CTX *mont,
122 BN_ULONG *ap,*np,*rp,n0,v,*nrp;
123 int al,nl,max,i,x,ri;
126 if ((r = BN_CTX_get(ctx)) == NULL) goto err;
128 if (!BN_copy(r,a)) goto err;
132 /* mont->ri is the size of mont->N in bits (rounded up
134 al=ri=mont->ri/BN_BITS2;
137 if ((al == 0) || (nl == 0)) { r->top=0; return(1); }
139 max=(nl+al+1); /* allow for overflow (no?) XXX */
140 if (bn_wexpand(r,max) == NULL) goto err;
141 if (bn_wexpand(ret,max) == NULL) goto err;
143 r->neg=a->neg^n->neg;
148 /* clear the top words of T */
150 for (i=r->top; i<max; i++) /* memset? XXX */
153 memset(&(r->d[r->top]),0,(max-r->top)*sizeof(BN_ULONG));
160 fprintf(stderr,"word BN_from_montgomery %d * %d\n",nl,nl);
169 t1 = rp[0] * (n0 & 0177777);
172 t3 = rp[0] & 0177777;
173 t2 = (t3 * t2) & BN_MASK2;
175 v=bn_mul_add_words(rp,np,nl,(BN_ULONG) t1);
178 v=bn_mul_add_words(rp,np,nl,(rp[0]*n0)&BN_MASK2);
182 if (((nrp[-1]+=v)&BN_MASK2) >= v)
186 if (((++nrp[0])&BN_MASK2) != 0) continue;
187 if (((++nrp[1])&BN_MASK2) != 0) continue;
188 for (x=2; (((++nrp[x])&BN_MASK2) == 0); x++) ;
193 /* mont->ri will be a multiple of the word size */
195 BN_rshift(ret,r,mont->ri);
207 for (i=0; i<al; i+=4)
209 BN_ULONG t1,t2,t3,t4;
224 #else /* !MONT_WORD */
228 t1 = BN_CTX_get(ctx);
229 t2 = BN_CTX_get(ctx);
230 if (t1 == NULL || t2 == NULL) goto err;
232 if (!BN_copy(t1,a)) goto err;
233 BN_mask_bits(t1,mont->ri);
235 if (!BN_mul(t2,t1,&mont->Ni,ctx)) goto err;
236 BN_mask_bits(t2,mont->ri);
238 if (!BN_mul(t1,t2,&mont->N,ctx)) goto err;
239 if (!BN_add(t2,a,t1)) goto err;
240 if (!BN_rshift(ret,t2,mont->ri)) goto err;
241 #endif /* MONT_WORD */
243 if (BN_ucmp(ret, &(mont->N)) >= 0)
245 if (!BN_usub(ret,ret,&(mont->N))) goto err;
254 BN_MONT_CTX *BN_MONT_CTX_new(void)
258 if ((ret=(BN_MONT_CTX *)OPENSSL_malloc(sizeof(BN_MONT_CTX))) == NULL)
261 BN_MONT_CTX_init(ret);
262 ret->flags=BN_FLG_MALLOCED;
266 void BN_MONT_CTX_init(BN_MONT_CTX *ctx)
275 void BN_MONT_CTX_free(BN_MONT_CTX *mont)
280 BN_free(&(mont->RR));
282 BN_free(&(mont->Ni));
283 if (mont->flags & BN_FLG_MALLOCED)
287 int BN_MONT_CTX_set(BN_MONT_CTX *mont, const BIGNUM *mod, BN_CTX *ctx)
293 if((Ri = BN_CTX_get(ctx)) == NULL) goto err;
294 R= &(mont->RR); /* grab RR as a temp */
295 if (!BN_copy(&(mont->N),mod)) goto err; /* Set N */
303 mont->ri=(BN_num_bits(mod)+(BN_BITS2-1))/BN_BITS2*BN_BITS2;
305 if (!(BN_set_bit(R,BN_BITS2))) goto err; /* R */
307 buf[0]=mod->d[0]; /* tmod = N mod word size */
310 tmod.top = buf[0] != 0 ? 1 : 0;
314 if ((BN_mod_inverse(Ri,R,&tmod,ctx)) == NULL)
316 if (!BN_lshift(Ri,Ri,BN_BITS2)) goto err; /* R*Ri */
319 if (!BN_sub_word(Ri,1)) goto err;
321 else /* if N mod word size == 1 */
323 if (!BN_set_word(Ri,BN_MASK2)) goto err; /* Ri-- (mod word size) */
325 if (!BN_div(Ri,NULL,Ri,&tmod,ctx)) goto err;
327 * keep only least significant word: */
328 mont->n0 = (Ri->top > 0) ? Ri->d[0] : 0;
330 #else /* !MONT_WORD */
331 { /* bignum version */
332 mont->ri=BN_num_bits(&mont->N);
334 if (!BN_set_bit(R,mont->ri)) goto err; /* R = 2^ri */
336 if ((BN_mod_inverse(Ri,R,&mont->N,ctx)) == NULL)
338 if (!BN_lshift(Ri,Ri,mont->ri)) goto err; /* R*Ri */
339 if (!BN_sub_word(Ri,1)) goto err;
340 /* Ni = (R*Ri-1) / N */
341 if (!BN_div(&(mont->Ni),NULL,Ri,&mont->N,ctx)) goto err;
345 /* setup RR for conversions */
346 BN_zero(&(mont->RR));
347 if (!BN_set_bit(&(mont->RR),mont->ri*2)) goto err;
348 if (!BN_mod(&(mont->RR),&(mont->RR),&(mont->N),ctx)) goto err;
356 BN_MONT_CTX *BN_MONT_CTX_copy(BN_MONT_CTX *to, BN_MONT_CTX *from)
358 if (to == from) return(to);
360 if (!BN_copy(&(to->RR),&(from->RR))) return NULL;
361 if (!BN_copy(&(to->N),&(from->N))) return NULL;
362 if (!BN_copy(&(to->Ni),&(from->Ni))) return NULL;
368 BN_MONT_CTX *BN_MONT_CTX_set_locked(BN_MONT_CTX **pmont, int lock,
369 const BIGNUM *mod, BN_CTX *ctx)
376 *pmont = BN_MONT_CTX_new();
377 if (*pmont && !BN_MONT_CTX_set(*pmont, mod, ctx))
379 BN_MONT_CTX_free(*pmont);
383 CRYPTO_w_unlock(lock);