1 /* crypto/bn/bn_exp.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) 1998-2000 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).
114 #include "cryptlib.h"
117 #define TABLE_SIZE 32
120 int BN_mod_mul(BIGNUM *ret, BIGNUM *a, BIGNUM *b, const BIGNUM *m, BN_CTX *ctx)
130 if ((t = BN_CTX_get(ctx)) == NULL) goto err;
132 { if (!BN_sqr(t,a,ctx)) goto err; }
134 { if (!BN_mul(t,a,b,ctx)) goto err; }
135 if (!BN_mod(ret,t,m,ctx)) goto err;
143 /* this one works - simple but works */
144 int BN_exp(BIGNUM *r, BIGNUM *a, BIGNUM *p, BN_CTX *ctx)
150 if ((r == a) || (r == p))
151 rr = BN_CTX_get(ctx);
154 if ((v = BN_CTX_get(ctx)) == NULL) goto err;
156 if (BN_copy(v,a) == NULL) goto err;
160 { if (BN_copy(rr,a) == NULL) goto err; }
161 else { if (!BN_one(rr)) goto err; }
163 for (i=1; i<bits; i++)
165 if (!BN_sqr(v,v,ctx)) goto err;
166 if (BN_is_bit_set(p,i))
168 if (!BN_mul(rr,rr,v,ctx)) goto err;
173 if (r != rr) BN_copy(r,rr);
179 int BN_mod_exp(BIGNUM *r, BIGNUM *a, const BIGNUM *p, const BIGNUM *m,
189 /* I have finally been able to take out this pre-condition of
190 * the top bit being set. It was caused by an error in BN_div
191 * with negatives. There was also another problem when for a^b%m
192 * a >= m. eay 07-May-97 */
193 /* if ((m->d[m->top-1]&BN_TBIT) && BN_is_odd(m)) */
199 BN_ULONG A = a->d[0];
200 ret=BN_mod_exp_mont_word(r,A,p,m,ctx,NULL);
203 ret=BN_mod_exp_mont(r,a,p,m,ctx,NULL);
208 { ret=BN_mod_exp_recp(r,a,p,m,ctx); }
210 { ret=BN_mod_exp_simple(r,a,p,m,ctx); }
217 int BN_mod_exp_recp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
218 const BIGNUM *m, BN_CTX *ctx)
220 int i,j,bits,ret=0,wstart,wend,window,wvalue;
223 BIGNUM val[TABLE_SIZE];
235 if ((aa = BN_CTX_get(ctx)) == NULL) goto err;
237 BN_RECP_CTX_init(&recp);
238 if (BN_RECP_CTX_set(&recp,m,ctx) <= 0) goto err;
243 if (!BN_mod(&(val[0]),a,m,ctx)) goto err; /* 1 */
245 window = BN_window_bits_for_exponent_size(bits);
248 if (!BN_mod_mul_reciprocal(aa,&(val[0]),&(val[0]),&recp,ctx))
254 if (!BN_mod_mul_reciprocal(&(val[i]),&(val[i-1]),aa,&recp,ctx))
260 start=1; /* This is used to avoid multiplication etc
261 * when there is only the value '1' in the
263 wvalue=0; /* The 'value' of the window */
264 wstart=bits-1; /* The top bit of the window */
265 wend=0; /* The bottom bit of the window */
267 if (!BN_one(r)) goto err;
271 if (BN_is_bit_set(p,wstart) == 0)
274 if (!BN_mod_mul_reciprocal(r,r,r,&recp,ctx))
276 if (wstart == 0) break;
280 /* We now have wstart on a 'set' bit, we now need to work out
281 * how bit a window to do. To do this we need to scan
282 * forward until the last set bit before the end of the
287 for (i=1; i<window; i++)
289 if (wstart-i < 0) break;
290 if (BN_is_bit_set(p,wstart-i))
298 /* wend is the size of the current window */
300 /* add the 'bytes above' */
304 if (!BN_mod_mul_reciprocal(r,r,r,&recp,ctx))
308 /* wvalue will be an odd number < 2^window */
309 if (!BN_mod_mul_reciprocal(r,r,&(val[wvalue>>1]),&recp,ctx))
312 /* move the 'window' down further */
316 if (wstart < 0) break;
322 BN_clear_free(&(val[i]));
323 BN_RECP_CTX_free(&recp);
328 int BN_mod_exp_mont(BIGNUM *rr, BIGNUM *a, const BIGNUM *p,
329 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *in_mont)
331 int i,j,bits,ret=0,wstart,wend,window,wvalue;
335 BIGNUM val[TABLE_SIZE];
336 BN_MONT_CTX *mont=NULL;
344 BNerr(BN_F_BN_MOD_EXP_MONT,BN_R_CALLED_WITH_EVEN_MODULUS);
356 if (d == NULL || r == NULL) goto err;
358 /* If this is not done, things will break in the montgomery
365 if ((mont=BN_MONT_CTX_new()) == NULL) goto err;
366 if (!BN_MONT_CTX_set(mont,m,ctx)) goto err;
371 if (BN_ucmp(a,m) >= 0)
373 if (!BN_mod(&(val[0]),a,m,ctx))
379 if (!BN_to_montgomery(&(val[0]),aa,mont,ctx)) goto err; /* 1 */
381 window = BN_window_bits_for_exponent_size(bits);
384 if (!BN_mod_mul_montgomery(d,&(val[0]),&(val[0]),mont,ctx)) goto err; /* 2 */
389 if (!BN_mod_mul_montgomery(&(val[i]),&(val[i-1]),d,mont,ctx))
395 start=1; /* This is used to avoid multiplication etc
396 * when there is only the value '1' in the
398 wvalue=0; /* The 'value' of the window */
399 wstart=bits-1; /* The top bit of the window */
400 wend=0; /* The bottom bit of the window */
402 if (!BN_to_montgomery(r,BN_value_one(),mont,ctx)) goto err;
405 if (BN_is_bit_set(p,wstart) == 0)
409 if (!BN_mod_mul_montgomery(r,r,r,mont,ctx))
412 if (wstart == 0) break;
416 /* We now have wstart on a 'set' bit, we now need to work out
417 * how bit a window to do. To do this we need to scan
418 * forward until the last set bit before the end of the
423 for (i=1; i<window; i++)
425 if (wstart-i < 0) break;
426 if (BN_is_bit_set(p,wstart-i))
434 /* wend is the size of the current window */
436 /* add the 'bytes above' */
440 if (!BN_mod_mul_montgomery(r,r,r,mont,ctx))
444 /* wvalue will be an odd number < 2^window */
445 if (!BN_mod_mul_montgomery(r,r,&(val[wvalue>>1]),mont,ctx))
448 /* move the 'window' down further */
452 if (wstart < 0) break;
454 if (!BN_from_montgomery(rr,r,mont,ctx)) goto err;
457 if ((in_mont == NULL) && (mont != NULL)) BN_MONT_CTX_free(mont);
460 BN_clear_free(&(val[i]));
464 int BN_mod_exp_mont_word(BIGNUM *rr, BN_ULONG a, const BIGNUM *p,
465 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *in_mont)
467 BN_MONT_CTX *mont = NULL;
473 #define BN_MOD_MUL_WORD(r, w, m) \
474 (BN_mul_word(r, (w)) && \
475 (/* BN_ucmp(r, (m)) < 0 ? 1 :*/ \
476 (BN_mod(t, r, m, ctx) && (swap_tmp = r, r = t, t = swap_tmp, 1))))
477 /* BN_MOD_MUL_WORD is only used with 'w' large,
478 * so the BN_ucmp test is probably more overhead
479 * than always using BN_mod (which uses BN_copy if
480 * a similar test returns true). */
481 #define BN_TO_MONTGOMERY_WORD(r, w, mont) \
482 (BN_set_word(r, (w)) && BN_to_montgomery(r, r, (mont), ctx))
489 BNerr(BN_F_BN_MOD_EXP_MONT_WORD,BN_R_CALLED_WITH_EVEN_MODULUS);
492 bits = BN_num_bits(p);
502 if (d == NULL || r == NULL || t == NULL) goto err;
508 if ((mont = BN_MONT_CTX_new()) == NULL) goto err;
509 if (!BN_MONT_CTX_set(mont, m, ctx)) goto err;
512 r_is_one = 1; /* except for Montgomery factor */
516 /* The result is accumulated in the product r*w. */
517 w = a; /* bit 'bits-1' of 'p' is always set */
518 for (b = bits-2; b >= 0; b--)
520 /* First, square r*w. */
522 if ((next_w/w) != w) /* overflow */
526 if (!BN_TO_MONTGOMERY_WORD(r, w, mont)) goto err;
531 if (!BN_MOD_MUL_WORD(r, w, m)) goto err;
538 if (!BN_mod_mul_montgomery(r, r, r, mont, ctx)) goto err;
541 /* Second, multiply r*w by 'a' if exponent bit is set. */
542 if (BN_is_bit_set(p, b))
545 if ((next_w/a) != w) /* overflow */
549 if (!BN_TO_MONTGOMERY_WORD(r, w, mont)) goto err;
554 if (!BN_MOD_MUL_WORD(r, w, m)) goto err;
562 /* Finally, set r:=r*w. */
567 if (!BN_TO_MONTGOMERY_WORD(r, w, mont)) goto err;
572 if (!BN_MOD_MUL_WORD(r, w, m)) goto err;
576 if (r_is_one) /* can happen only if a == 1*/
578 if (!BN_one(rr)) goto err;
582 if (!BN_from_montgomery(rr, r, mont, ctx)) goto err;
586 if ((in_mont == NULL) && (mont != NULL)) BN_MONT_CTX_free(mont);
592 /* The old fallback, simple version :-) */
593 int BN_mod_exp_simple(BIGNUM *r, BIGNUM *a, BIGNUM *p, BIGNUM *m,
596 int i,j,bits,ret=0,wstart,wend,window,wvalue,ts=0;
599 BIGNUM val[TABLE_SIZE];
610 if ((d = BN_CTX_get(ctx)) == NULL) goto err;
614 if (!BN_mod(&(val[0]),a,m,ctx)) goto err; /* 1 */
616 window = BN_window_bits_for_exponent_size(bits);
619 if (!BN_mod_mul(d,&(val[0]),&(val[0]),m,ctx))
625 if (!BN_mod_mul(&(val[i]),&(val[i-1]),d,m,ctx))
631 start=1; /* This is used to avoid multiplication etc
632 * when there is only the value '1' in the
634 wvalue=0; /* The 'value' of the window */
635 wstart=bits-1; /* The top bit of the window */
636 wend=0; /* The bottom bit of the window */
638 if (!BN_one(r)) goto err;
642 if (BN_is_bit_set(p,wstart) == 0)
645 if (!BN_mod_mul(r,r,r,m,ctx))
647 if (wstart == 0) break;
651 /* We now have wstart on a 'set' bit, we now need to work out
652 * how bit a window to do. To do this we need to scan
653 * forward until the last set bit before the end of the
658 for (i=1; i<window; i++)
660 if (wstart-i < 0) break;
661 if (BN_is_bit_set(p,wstart-i))
669 /* wend is the size of the current window */
671 /* add the 'bytes above' */
675 if (!BN_mod_mul(r,r,r,m,ctx))
679 /* wvalue will be an odd number < 2^window */
680 if (!BN_mod_mul(r,r,&(val[wvalue>>1]),m,ctx))
683 /* move the 'window' down further */
687 if (wstart < 0) break;
693 BN_clear_free(&(val[i]));