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, BIGNUM *a, BIGNUM *b,
73 BN_MONT_CTX *mont, BN_CTX *ctx)
78 tmp = BN_CTX_get(ctx);
79 tmp2 = BN_CTX_get(ctx);
80 if (tmp == NULL || tmp2 == NULL) goto err;
88 bn_wexpand(tmp,a->top*2);
89 bn_wexpand(tmp2,a->top*4);
90 bn_sqr_recursive(tmp->d,a->d,a->top,tmp2->d);
92 if (tmp->d[tmp->top-1] == 0)
95 if (!BN_sqr(tmp,a,ctx)) goto err;
100 if (!BN_mul(tmp,a,b,ctx)) goto err;
102 /* reduce from aRR to aR */
103 if (!BN_from_montgomery(r,tmp,mont,ctx)) goto err;
110 int BN_from_montgomery(BIGNUM *ret, BIGNUM *a, BN_MONT_CTX *mont,
117 BN_ULONG *ap,*np,*rp,n0,v,*nrp;
118 int al,nl,max,i,x,ri;
121 if ((r = BN_CTX_get(ctx)) == NULL) goto err;
123 if (!BN_copy(r,a)) goto err;
127 /* mont->ri is the size of mont->N in bits (rounded up
129 al=ri=mont->ri/BN_BITS2;
132 if ((al == 0) || (nl == 0)) { r->top=0; return(1); }
134 max=(nl+al+1); /* allow for overflow (no?) XXX */
135 if (bn_wexpand(r,max) == NULL) goto err;
136 if (bn_wexpand(ret,max) == NULL) goto err;
138 r->neg=a->neg^n->neg;
143 /* clear the top words of T */
145 for (i=r->top; i<max; i++) /* memset? XXX */
148 memset(&(r->d[r->top]),0,(max-r->top)*sizeof(BN_ULONG));
155 printf("word BN_from_montgomery %d * %d\n",nl,nl);
159 v=bn_mul_add_words(rp,np,nl,(rp[0]*n0)&BN_MASK2);
162 if (((nrp[-1]+=v)&BN_MASK2) >= v)
166 if (((++nrp[0])&BN_MASK2) != 0) continue;
167 if (((++nrp[1])&BN_MASK2) != 0) continue;
168 for (x=2; (((++nrp[x])&BN_MASK2) == 0); x++) ;
173 /* mont->ri will be a multiple of the word size */
175 BN_rshift(ret,r,mont->ri);
186 for (i=0; i<al; i+=4)
188 BN_ULONG t1,t2,t3,t4;
203 #else /* !MONT_WORD */
207 t1 = BN_CTX_get(ctx);
208 t2 = BN_CTX_get(ctx);
209 if (t1 == NULL || t2 == NULL) goto err;
211 if (!BN_copy(t1,a)) goto err;
212 BN_mask_bits(t1,mont->ri);
214 if (!BN_mul(t2,t1,&mont->Ni,ctx)) goto err;
215 BN_mask_bits(t2,mont->ri);
217 if (!BN_mul(t1,t2,&mont->N,ctx)) goto err;
218 if (!BN_add(t2,a,t1)) goto err;
219 BN_rshift(ret,t2,mont->ri);
220 #endif /* MONT_WORD */
222 if (BN_ucmp(ret, &(mont->N)) >= 0)
224 BN_usub(ret,ret,&(mont->N));
232 BN_MONT_CTX *BN_MONT_CTX_new(void)
236 if ((ret=(BN_MONT_CTX *)Malloc(sizeof(BN_MONT_CTX))) == NULL)
239 BN_MONT_CTX_init(ret);
240 ret->flags=BN_FLG_MALLOCED;
244 void BN_MONT_CTX_init(BN_MONT_CTX *ctx)
253 void BN_MONT_CTX_free(BN_MONT_CTX *mont)
258 BN_free(&(mont->RR));
260 BN_free(&(mont->Ni));
261 if (mont->flags & BN_FLG_MALLOCED)
265 int BN_MONT_CTX_set(BN_MONT_CTX *mont, const BIGNUM *mod, BN_CTX *ctx)
270 R= &(mont->RR); /* grab RR as a temp */
271 BN_copy(&(mont->N),mod); /* Set N */
278 mont->ri=(BN_num_bits(mod)+(BN_BITS2-1))/BN_BITS2*BN_BITS2;
280 BN_set_bit(R,BN_BITS2); /* R */
282 buf[0]=mod->d[0]; /* tmod = N mod word size */
289 if ((BN_mod_inverse(&Ri,R,&tmod,ctx)) == NULL)
291 BN_lshift(&Ri,&Ri,BN_BITS2); /* R*Ri */
292 if (!BN_is_zero(&Ri))
294 else /* if N mod word size == 1 */
295 BN_set_word(&Ri,BN_MASK2); /* Ri-- (mod word size) */
296 BN_div(&Ri,NULL,&Ri,&tmod,ctx); /* Ni = (R*Ri-1)/N,
297 * keep only least significant word: */
301 #else /* !MONT_WORD */
302 { /* bignum version */
303 mont->ri=BN_num_bits(mod);
305 BN_set_bit(R,mont->ri); /* R = 2^ri */
307 if ((BN_mod_inverse(&Ri,R,mod,ctx)) == NULL)
309 BN_lshift(&Ri,&Ri,mont->ri); /* R*Ri */
311 /* Ni = (R*Ri-1) / N */
312 BN_div(&(mont->Ni),NULL,&Ri,mod,ctx);
317 /* setup RR for conversions */
318 BN_zero(&(mont->RR));
319 BN_set_bit(&(mont->RR),mont->ri*2);
320 BN_mod(&(mont->RR),&(mont->RR),&(mont->N),ctx);
327 BN_MONT_CTX *BN_MONT_CTX_copy(BN_MONT_CTX *to, BN_MONT_CTX *from)
329 if (to == from) return(to);
331 BN_copy(&(to->RR),&(from->RR));
332 BN_copy(&(to->N),&(from->N));
333 BN_copy(&(to->Ni),&(from->Ni));