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)
79 tmp = BN_CTX_get(ctx);
80 tmp2 = BN_CTX_get(ctx);
81 if (tmp == NULL || tmp2 == NULL) goto err;
89 bn_wexpand(tmp,a->top*2);
90 bn_wexpand(tmp2,a->top*4);
91 bn_sqr_recursive(tmp->d,a->d,a->top,tmp2->d);
93 if (tmp->d[tmp->top-1] == 0)
96 if (!BN_sqr(tmp,a,ctx)) goto err;
101 if (!BN_mul(tmp,a,b,ctx)) goto err;
103 /* reduce from aRR to aR */
104 if (!BN_from_montgomery(r,tmp,mont,ctx)) goto err;
111 int BN_from_montgomery(BIGNUM *ret, BIGNUM *a, BN_MONT_CTX *mont,
118 BN_ULONG *ap,*np,*rp,n0,v,*nrp;
119 int al,nl,max,i,x,ri;
122 if ((r = BN_CTX_get(ctx)) == NULL) goto err;
124 if (!BN_copy(r,a)) goto err;
128 /* mont->ri is the size of mont->N in bits (rounded up
130 al=ri=mont->ri/BN_BITS2;
133 if ((al == 0) || (nl == 0)) { r->top=0; return(1); }
135 max=(nl+al+1); /* allow for overflow (no?) XXX */
136 if (bn_wexpand(r,max) == NULL) goto err;
137 if (bn_wexpand(ret,max) == NULL) goto err;
139 r->neg=a->neg^n->neg;
144 /* clear the top words of T */
146 for (i=r->top; i<max; i++) /* memset? XXX */
149 memset(&(r->d[r->top]),0,(max-r->top)*sizeof(BN_ULONG));
156 printf("word BN_from_montgomery %d * %d\n",nl,nl);
160 v=bn_mul_add_words(rp,np,nl,(rp[0]*n0)&BN_MASK2);
163 if (((nrp[-1]+=v)&BN_MASK2) >= v)
167 if (((++nrp[0])&BN_MASK2) != 0) continue;
168 if (((++nrp[1])&BN_MASK2) != 0) continue;
169 for (x=2; (((++nrp[x])&BN_MASK2) == 0); x++) ;
174 /* mont->ri will be a multiple of the word size */
176 BN_rshift(ret,r,mont->ri);
187 for (i=0; i<al; i+=4)
189 BN_ULONG t1,t2,t3,t4;
204 #else /* !MONT_WORD */
208 t1 = BN_CTX_get(ctx);
209 t2 = BN_CTX_get(ctx);
210 if (t1 == NULL || t2 == NULL) goto err;
212 if (!BN_copy(t1,a)) goto err;
213 BN_mask_bits(t1,mont->ri);
215 if (!BN_mul(t2,t1,&mont->Ni,ctx)) goto err;
216 BN_mask_bits(t2,mont->ri);
218 if (!BN_mul(t1,t2,&mont->N,ctx)) goto err;
219 if (!BN_add(t2,a,t1)) goto err;
220 BN_rshift(ret,t2,mont->ri);
221 #endif /* MONT_WORD */
223 if (BN_ucmp(ret, &(mont->N)) >= 0)
225 BN_usub(ret,ret,&(mont->N));
233 BN_MONT_CTX *BN_MONT_CTX_new(void)
237 if ((ret=(BN_MONT_CTX *)Malloc(sizeof(BN_MONT_CTX))) == NULL)
240 BN_MONT_CTX_init(ret);
241 ret->flags=BN_FLG_MALLOCED;
245 void BN_MONT_CTX_init(BN_MONT_CTX *ctx)
254 void BN_MONT_CTX_free(BN_MONT_CTX *mont)
259 BN_free(&(mont->RR));
261 BN_free(&(mont->Ni));
262 if (mont->flags & BN_FLG_MALLOCED)
266 int BN_MONT_CTX_set(BN_MONT_CTX *mont, const BIGNUM *mod, BN_CTX *ctx)
271 R= &(mont->RR); /* grab RR as a temp */
272 BN_copy(&(mont->N),mod); /* Set N */
279 mont->ri=(BN_num_bits(mod)+(BN_BITS2-1))/BN_BITS2*BN_BITS2;
281 BN_set_bit(R,BN_BITS2); /* R */
283 buf[0]=mod->d[0]; /* tmod = N mod word size */
290 if ((BN_mod_inverse(&Ri,R,&tmod,ctx)) == NULL)
292 BN_lshift(&Ri,&Ri,BN_BITS2); /* R*Ri */
293 if (!BN_is_zero(&Ri))
295 else /* if N mod word size == 1 */
296 BN_set_word(&Ri,BN_MASK2); /* Ri-- (mod word size) */
297 BN_div(&Ri,NULL,&Ri,&tmod,ctx); /* Ni = (R*Ri-1)/N,
298 * keep only least significant word: */
302 #else /* !MONT_WORD */
303 { /* bignum version */
304 mont->ri=BN_num_bits(mod);
306 BN_set_bit(R,mont->ri); /* R = 2^ri */
308 if ((BN_mod_inverse(&Ri,R,mod,ctx)) == NULL)
310 BN_lshift(&Ri,&Ri,mont->ri); /* R*Ri */
312 /* Ni = (R*Ri-1) / N */
313 BN_div(&(mont->Ni),NULL,&Ri,mod,ctx);
318 /* setup RR for conversions */
319 BN_zero(&(mont->RR));
320 BN_set_bit(&(mont->RR),mont->ri*2);
321 BN_mod(&(mont->RR),&(mont->RR),&(mont->N),ctx);
328 BN_MONT_CTX *BN_MONT_CTX_copy(BN_MONT_CTX *to, BN_MONT_CTX *from)
330 if (to == from) return(to);
332 BN_copy(&(to->RR),&(from->RR));
333 BN_copy(&(to->N),&(from->N));
334 BN_copy(&(to->Ni),&(from->Ni));