1 /* crypto/bn/bn_mont.c */
2 /* Copyright (C) 1995-1997 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.]
63 int BN_mod_mul_montgomery(r,a,b,mont,ctx)
70 tmp=ctx->bn[ctx->tos++];
74 if (!BN_sqr(tmp,a,ctx)) goto err;
78 if (!BN_mul(tmp,a,b)) goto err;
80 /* reduce from aRR to aR */
81 if (!BN_from_montgomery(r,tmp,mont,ctx)) goto err;
91 int BN_from_montgomery(ret,a,mont,ctx)
98 BN_ULONG *ap,*np,*rp,k,n0,v,v2;
102 t1=ctx->bn[ctx->tos];
103 r=ctx->bn[ctx->tos+1];
105 if (!BN_copy(r,a)) goto err;
108 if (!BN_copy(t1,a)) goto err;
109 BN_mask_bits(t1,mont->ri);
115 if ((al == 0) || (nl == 0)) { r->top=0; return(1); }
117 max=(nl+al+1); /* allow for overflow (no?) XXX */
118 if (bn_expand(r,(max)*BN_BITS2) == NULL) goto err;
120 r->neg=a->neg^n->neg;
125 /* clear the top bytes of T */
126 for (i=r->top; i<max; i++) /* memset? XXX */
128 /* memset(&(r->d[r->top]),0,(max-r->top)*sizeof(BN_ULONG)); */
135 /* This is were part words probably goes wrong */
136 k=(rp[0]*n0)&BN_MASK2;
137 v=bn_mul_add_word(rp,np,nl,k);
144 v=((v2&BN_MASK2) < v)?1:0; /* ever true? XXX */
148 while (r->d[r->top-1] == 0)
151 BN_rshift(ret,r,mont->ri);
153 if (BN_ucmp(ret,mont->N) >= 0)
155 bn_qsub(ret,ret,mont->N); /* XXX */
162 int BN_from_montgomery(r,a,mont,ctx)
170 t1=ctx->bn[ctx->tos];
171 t2=ctx->bn[ctx->tos+1];
173 if (!BN_copy(t1,a)) goto err;
175 BN_mask_bits(t1,mont->ri);
177 if (!BN_mul(t2,t1,mont->Ni)) goto err;
178 BN_mask_bits(t2,mont->ri);
180 if (!BN_mul(t1,t2,mont->N)) goto err;
181 if (!BN_add(t2,a,t1)) goto err;
182 BN_rshift(r,t2,mont->ri);
184 if (BN_ucmp(r,mont->N) >= 0)
185 bn_qsub(r,r,mont->N);
193 BN_MONT_CTX *BN_MONT_CTX_new()
197 if ((ret=(BN_MONT_CTX *)Malloc(sizeof(BN_MONT_CTX))) == NULL)
203 if ((ret->RR == NULL) || (ret->N == NULL))
205 BN_MONT_CTX_free(ret);
211 void BN_MONT_CTX_free(mont)
214 if (mont->RR != NULL) BN_free(mont->RR);
215 if (mont->N != NULL) BN_free(mont->N);
216 if (mont->Ni != NULL) BN_free(mont->Ni);
220 int BN_MONT_CTX_set(mont,mod,ctx)
225 BIGNUM *Ri=NULL,*R=NULL;
227 if (mont->RR == NULL) mont->RR=BN_new();
228 if (mont->N == NULL) mont->N=BN_new();
230 R=mont->RR; /* grab RR as a temp */
231 BN_copy(mont->N,mod); /* Set N */
239 mont->ri=(BN_num_bits(mod)+(BN_BITS2-1))/BN_BITS2*BN_BITS2;
240 BN_lshift(R,BN_value_one(),BN_BITS2); /* R */
241 /* I was bad, this modification of a passed variable was
242 * breaking the multithreaded stuff :-(
253 if ((Ri=BN_mod_inverse(R,&tmod,ctx)) == NULL) goto err; /* Ri */
254 BN_lshift(Ri,Ri,BN_BITS2); /* R*Ri */
255 bn_qsub(Ri,Ri,BN_value_one()); /* R*Ri - 1 */
256 BN_div(Ri,NULL,Ri,&tmod,ctx);
262 mont->ri=BN_num_bits(mod);
263 BN_lshift(R,BN_value_one(),mont->ri); /* R */
264 if ((Ri=BN_mod_inverse(R,mod,ctx)) == NULL) goto err; /* Ri */
265 BN_lshift(Ri,Ri,mont->ri); /* R*Ri */
266 bn_qsub(Ri,Ri,BN_value_one()); /* R*Ri - 1 */
267 BN_div(Ri,NULL,Ri,mod,ctx);
268 if (mont->Ni != NULL) BN_free(mont->Ni);
269 mont->Ni=Ri; /* Ni=(R*Ri-1)/N */
272 /* setup RR for conversions */
273 BN_lshift(mont->RR,BN_value_one(),mont->ri*2);
274 BN_mod(mont->RR,mont->RR,mont->N,ctx);