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) 1998-2005 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).
113 #include "cryptlib.h"
120 # define alloca _alloca
122 #elif defined(__GNUC__)
124 # define alloca(s) __builtin_alloca((s))
128 #if defined(OPENSSL_BN_ASM_MONT) && (defined(__sparc__) || defined(__sparc))
129 # include "sparc_arch.h"
130 extern unsigned int OPENSSL_sparcv9cap_P[];
133 /* maximum precomputation table size for *variable* sliding windows */
134 #define TABLE_SIZE 32
136 /* this one works - simple but works */
137 int BN_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
142 if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0)
144 /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */
145 BNerr(BN_F_BN_EXP,ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
150 if ((r == a) || (r == p))
151 rr = BN_CTX_get(ctx);
155 if (rr == NULL || v == NULL) goto err;
157 if (BN_copy(v,a) == NULL) goto err;
161 { if (BN_copy(rr,a) == NULL) goto err; }
162 else { if (!BN_one(rr)) goto err; }
164 for (i=1; i<bits; i++)
166 if (!BN_sqr(v,v,ctx)) goto err;
167 if (BN_is_bit_set(p,i))
169 if (!BN_mul(rr,rr,v,ctx)) goto err;
174 if (r != rr) BN_copy(r,rr);
181 int BN_mod_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m,
190 /* For even modulus m = 2^k*m_odd, it might make sense to compute
191 * a^p mod m_odd and a^p mod 2^k separately (with Montgomery
192 * exponentiation for the odd part), using appropriate exponent
193 * reductions, and combine the results using the CRT.
195 * For now, we use Montgomery only if the modulus is odd; otherwise,
196 * exponentiation using the reciprocal-based quick remaindering
199 * (Timing obtained with expspeed.c [computations a^p mod m
200 * where a, p, m are of the same length: 256, 512, 1024, 2048,
201 * 4096, 8192 bits], compared to the running time of the
202 * standard algorithm:
204 * BN_mod_exp_mont 33 .. 40 % [AMD K6-2, Linux, debug configuration]
205 * 55 .. 77 % [UltraSparc processor, but
206 * debug-solaris-sparcv8-gcc conf.]
208 * BN_mod_exp_recp 50 .. 70 % [AMD K6-2, Linux, debug configuration]
209 * 62 .. 118 % [UltraSparc, debug-solaris-sparcv8-gcc]
211 * On the Sparc, BN_mod_exp_recp was faster than BN_mod_exp_mont
212 * at 2048 and more bits, but at 512 and 1024 bits, it was
213 * slower even than the standard algorithm!
215 * "Real" timings [linux-elf, solaris-sparcv9-gcc configurations]
216 * should be obtained when the new Montgomery reduction code
217 * has been integrated into OpenSSL.)
221 #define MONT_EXP_WORD
225 /* I have finally been able to take out this pre-condition of
226 * the top bit being set. It was caused by an error in BN_div
227 * with negatives. There was also another problem when for a^b%m
228 * a >= m. eay 07-May-97 */
229 /* if ((m->d[m->top-1]&BN_TBIT) && BN_is_odd(m)) */
233 # ifdef MONT_EXP_WORD
234 if (a->top == 1 && !a->neg && (BN_get_flags(p, BN_FLG_CONSTTIME) == 0))
236 BN_ULONG A = a->d[0];
237 ret=BN_mod_exp_mont_word(r,A,p,m,ctx,NULL);
241 ret=BN_mod_exp_mont(r,a,p,m,ctx,NULL);
246 { ret=BN_mod_exp_recp(r,a,p,m,ctx); }
248 { ret=BN_mod_exp_simple(r,a,p,m,ctx); }
256 int BN_mod_exp_recp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
257 const BIGNUM *m, BN_CTX *ctx)
259 int i,j,bits,ret=0,wstart,wend,window,wvalue;
262 /* Table of variables obtained from 'ctx' */
263 BIGNUM *val[TABLE_SIZE];
266 if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0)
268 /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */
269 BNerr(BN_F_BN_MOD_EXP_RECP,ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
282 aa = BN_CTX_get(ctx);
283 val[0] = BN_CTX_get(ctx);
284 if(!aa || !val[0]) goto err;
286 BN_RECP_CTX_init(&recp);
289 /* ignore sign of 'm' */
290 if (!BN_copy(aa, m)) goto err;
292 if (BN_RECP_CTX_set(&recp,aa,ctx) <= 0) goto err;
296 if (BN_RECP_CTX_set(&recp,m,ctx) <= 0) goto err;
299 if (!BN_nnmod(val[0],a,m,ctx)) goto err; /* 1 */
300 if (BN_is_zero(val[0]))
307 window = BN_window_bits_for_exponent_size(bits);
310 if (!BN_mod_mul_reciprocal(aa,val[0],val[0],&recp,ctx))
315 if(((val[i] = BN_CTX_get(ctx)) == NULL) ||
316 !BN_mod_mul_reciprocal(val[i],val[i-1],
322 start=1; /* This is used to avoid multiplication etc
323 * when there is only the value '1' in the
325 wvalue=0; /* The 'value' of the window */
326 wstart=bits-1; /* The top bit of the window */
327 wend=0; /* The bottom bit of the window */
329 if (!BN_one(r)) goto err;
333 if (BN_is_bit_set(p,wstart) == 0)
336 if (!BN_mod_mul_reciprocal(r,r,r,&recp,ctx))
338 if (wstart == 0) break;
342 /* We now have wstart on a 'set' bit, we now need to work out
343 * how bit a window to do. To do this we need to scan
344 * forward until the last set bit before the end of the
349 for (i=1; i<window; i++)
351 if (wstart-i < 0) break;
352 if (BN_is_bit_set(p,wstart-i))
360 /* wend is the size of the current window */
362 /* add the 'bytes above' */
366 if (!BN_mod_mul_reciprocal(r,r,r,&recp,ctx))
370 /* wvalue will be an odd number < 2^window */
371 if (!BN_mod_mul_reciprocal(r,r,val[wvalue>>1],&recp,ctx))
374 /* move the 'window' down further */
378 if (wstart < 0) break;
383 BN_RECP_CTX_free(&recp);
389 int BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p,
390 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *in_mont)
392 int i,j,bits,ret=0,wstart,wend,window,wvalue;
396 /* Table of variables obtained from 'ctx' */
397 BIGNUM *val[TABLE_SIZE];
398 BN_MONT_CTX *mont=NULL;
400 if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0)
402 return BN_mod_exp_mont_consttime(rr, a, p, m, ctx, in_mont);
411 BNerr(BN_F_BN_MOD_EXP_MONT,BN_R_CALLED_WITH_EVEN_MODULUS);
424 val[0] = BN_CTX_get(ctx);
425 if (!d || !r || !val[0]) goto err;
427 /* If this is not done, things will break in the montgomery
434 if ((mont=BN_MONT_CTX_new()) == NULL) goto err;
435 if (!BN_MONT_CTX_set(mont,m,ctx)) goto err;
438 if (a->neg || BN_ucmp(a,m) >= 0)
440 if (!BN_nnmod(val[0],a,m,ctx))
452 if (!BN_to_montgomery(val[0],aa,mont,ctx)) goto err; /* 1 */
454 window = BN_window_bits_for_exponent_size(bits);
457 if (!BN_mod_mul_montgomery(d,val[0],val[0],mont,ctx)) goto err; /* 2 */
461 if(((val[i] = BN_CTX_get(ctx)) == NULL) ||
462 !BN_mod_mul_montgomery(val[i],val[i-1],
468 start=1; /* This is used to avoid multiplication etc
469 * when there is only the value '1' in the
471 wvalue=0; /* The 'value' of the window */
472 wstart=bits-1; /* The top bit of the window */
473 wend=0; /* The bottom bit of the window */
475 if (!BN_to_montgomery(r,BN_value_one(),mont,ctx)) goto err;
478 if (BN_is_bit_set(p,wstart) == 0)
482 if (!BN_mod_mul_montgomery(r,r,r,mont,ctx))
485 if (wstart == 0) break;
489 /* We now have wstart on a 'set' bit, we now need to work out
490 * how bit a window to do. To do this we need to scan
491 * forward until the last set bit before the end of the
496 for (i=1; i<window; i++)
498 if (wstart-i < 0) break;
499 if (BN_is_bit_set(p,wstart-i))
507 /* wend is the size of the current window */
509 /* add the 'bytes above' */
513 if (!BN_mod_mul_montgomery(r,r,r,mont,ctx))
517 /* wvalue will be an odd number < 2^window */
518 if (!BN_mod_mul_montgomery(r,r,val[wvalue>>1],mont,ctx))
521 /* move the 'window' down further */
525 if (wstart < 0) break;
527 if (!BN_from_montgomery(rr,r,mont,ctx)) goto err;
530 if ((in_mont == NULL) && (mont != NULL)) BN_MONT_CTX_free(mont);
537 /* BN_mod_exp_mont_consttime() stores the precomputed powers in a specific layout
538 * so that accessing any of these table values shows the same access pattern as far
539 * as cache lines are concerned. The following functions are used to transfer a BIGNUM
540 * from/to that table. */
542 static int MOD_EXP_CTIME_COPY_TO_PREBUF(const BIGNUM *b, int top, unsigned char *buf, int idx, int width)
547 top = b->top; /* this works because 'buf' is explicitly zeroed */
548 for (i = 0, j=idx; i < top * sizeof b->d[0]; i++, j+=width)
550 buf[j] = ((unsigned char*)b->d)[i];
556 static int MOD_EXP_CTIME_COPY_FROM_PREBUF(BIGNUM *b, int top, unsigned char *buf, int idx, int width)
560 if (bn_wexpand(b, top) == NULL)
563 for (i=0, j=idx; i < top * sizeof b->d[0]; i++, j+=width)
565 ((unsigned char*)b->d)[i] = buf[j];
573 /* Given a pointer value, compute the next address that is a cache line multiple. */
574 #define MOD_EXP_CTIME_ALIGN(x_) \
575 ((unsigned char*)(x_) + (MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH - (((size_t)(x_)) & (MOD_EXP_CTIME_MIN_CACHE_LINE_MASK))))
577 /* This variant of BN_mod_exp_mont() uses fixed windows and the special
578 * precomputation memory layout to limit data-dependency to a minimum
579 * to protect secret exponents (cf. the hyper-threading timing attacks
580 * pointed out by Colin Percival,
581 * http://www.daemonology.net/hyperthreading-considered-harmful/)
583 int BN_mod_exp_mont_consttime(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p,
584 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *in_mont)
586 int i,bits,ret=0,window,wvalue;
588 BN_MONT_CTX *mont=NULL;
591 unsigned char *powerbufFree=NULL;
593 unsigned char *powerbuf=NULL;
595 #if defined(OPENSSL_BN_ASM_MONT) && (defined(__sparc__) || defined(__sparc))
607 BNerr(BN_F_BN_MOD_EXP_MONT_CONSTTIME,BN_R_CALLED_WITH_EVEN_MODULUS);
619 /* Allocate a montgomery context if it was not supplied by the caller.
620 * If this is not done, things will break in the montgomery part.
626 if ((mont=BN_MONT_CTX_new()) == NULL) goto err;
627 if (!BN_MONT_CTX_set(mont,m,ctx)) goto err;
630 /* Get the window size to use with size of p. */
631 window = BN_window_bits_for_ctime_exponent_size(bits);
632 #if defined(OPENSSL_BN_ASM_MONT) && (defined(__sparc__) || defined(__sparc))
633 if (window>=5 && (top&15)==0 && top<=64 &&
634 (OPENSSL_sparcv9cap_P[1]&(CFR_MONTMUL|CFR_MONTSQR))==
635 (CFR_MONTMUL|CFR_MONTSQR) &&
636 (t4=OPENSSL_sparcv9cap_P[0]))
640 #if defined(OPENSSL_BN_ASM_MONT5)
641 if (window==6 && bits<=1024) window=5; /* ~5% improvement of 2048-bit RSA sign */
645 /* Allocate a buffer large enough to hold all of the pre-computed
646 * powers of am, am itself and tmp.
648 numPowers = 1 << window;
649 powerbufLen = sizeof(m->d[0])*(top*numPowers +
650 ((2*top)>numPowers?(2*top):numPowers));
652 if (powerbufLen < 3072)
653 powerbufFree = alloca(powerbufLen+MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH);
656 if ((powerbufFree=(unsigned char*)OPENSSL_malloc(powerbufLen+MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH)) == NULL)
659 powerbuf = MOD_EXP_CTIME_ALIGN(powerbufFree);
660 memset(powerbuf, 0, powerbufLen);
663 if (powerbufLen < 3072)
667 /* lay down tmp and am right after powers table */
668 tmp.d = (BN_ULONG *)(powerbuf + sizeof(m->d[0])*top*numPowers);
670 tmp.top = am.top = 0;
671 tmp.dmax = am.dmax = top;
672 tmp.neg = am.neg = 0;
673 tmp.flags = am.flags = BN_FLG_STATIC_DATA;
675 /* prepare a^0 in Montgomery domain */
677 if (!BN_to_montgomery(&tmp,BN_value_one(),mont,ctx)) goto err;
679 tmp.d[0] = (0-m->d[0])&BN_MASK2; /* 2^(top*BN_BITS2) - m */
681 tmp.d[i] = (~m->d[i])&BN_MASK2;
685 /* prepare a^1 in Montgomery domain */
686 if (a->neg || BN_ucmp(a,m) >= 0)
688 if (!BN_mod(&am,a,m,ctx)) goto err;
689 if (!BN_to_montgomery(&am,&am,mont,ctx)) goto err;
691 else if (!BN_to_montgomery(&am,a,mont,ctx)) goto err;
693 #if defined(OPENSSL_BN_ASM_MONT) && (defined(__sparc__) || defined(__sparc))
696 typedef int (*bn_pwr5_mont_f)(BN_ULONG *tp,const BN_ULONG *np,
697 const BN_ULONG *n0,const void *table,int power);
698 int bn_pwr5_mont_t4_8(BN_ULONG *tp,const BN_ULONG *np,
699 const BN_ULONG *n0,const void *table,int power);
700 int bn_pwr5_mont_t4_16(BN_ULONG *tp,const BN_ULONG *np,
701 const BN_ULONG *n0,const void *table,int power);
702 int bn_pwr5_mont_t4_24(BN_ULONG *tp,const BN_ULONG *np,
703 const BN_ULONG *n0,const void *table,int power);
704 int bn_pwr5_mont_t4_32(BN_ULONG *tp,const BN_ULONG *np,
705 const BN_ULONG *n0,const void *table,int power);
706 static const bn_pwr5_mont_f funcs[4] = {
707 bn_pwr5_mont_t4_8, bn_pwr5_mont_t4_16,
708 bn_pwr5_mont_t4_24, bn_pwr5_mont_t4_32 };
709 bn_pwr5_mont_f worker = funcs[top/16-1];
711 void bn_mul_mont_t4(BN_ULONG *rp,const BN_ULONG *ap,
712 const void *bp,const BN_ULONG *np,
713 const BN_ULONG *n0,int num);
714 void bn_mul_mont_gather5_t4(BN_ULONG *rp,const BN_ULONG *ap,
715 const void *table,const BN_ULONG *np,
716 const BN_ULONG *n0,int num,int power);
717 void bn_scatter5_t4(const BN_ULONG *inp,size_t num,
718 void *table,size_t power);
719 void bn_gather5_t4(BN_ULONG *out,size_t num,
720 void *table,size_t power);
721 void bn_flip_t4(BN_ULONG *dst,BN_ULONG *src,size_t num);
723 BN_ULONG *np=alloca(top*sizeof(BN_ULONG)), *n0=mont->n0;
725 /* BN_to_montgomery can contaminate words above .top
726 * [in BN_DEBUG[_DEBUG] build]... */
727 for (i=am.top; i<top; i++) am.d[i]=0;
728 for (i=tmp.top; i<top; i++) tmp.d[i]=0;
730 /* switch to 64-bit domain */
732 bn_flip_t4(np,mont->N.d,top);
733 bn_flip_t4(tmp.d,tmp.d,top);
734 bn_flip_t4(am.d,am.d,top);
736 bn_scatter5_t4(tmp.d,top,powerbuf,0);
737 bn_scatter5_t4(am.d,top,powerbuf,1);
738 bn_mul_mont_t4(tmp.d,am.d,am.d,np,n0,top);
739 bn_scatter5_t4(tmp.d,top,powerbuf,2);
743 /* Calculate a^i = a^(i-1) * a */
744 bn_mul_mont_gather5_t4(tmp.d,am.d,powerbuf,np,n0,top,i-1);
745 bn_scatter5_t4(tmp.d,top,powerbuf,i);
749 for (wvalue=0, i=bits%5; i>=0; i--,bits--)
750 wvalue = (wvalue<<1)+BN_is_bit_set(p,bits);
751 bn_gather5_t4(tmp.d,top,powerbuf,wvalue);
753 /* Scan the exponent one window at a time starting from the most
758 for (wvalue=0, i=0; i<5; i++,bits--)
759 wvalue = (wvalue<<1)+BN_is_bit_set(p,bits);
761 if ((*worker)(tmp.d,np,n0,powerbuf,wvalue)) continue;
762 /* retry once and fall back */
763 if ((*worker)(tmp.d,np,n0,powerbuf,wvalue)) continue;
764 bn_mul_mont_t4(tmp.d,tmp.d,tmp.d,np,n0,top);
765 bn_mul_mont_t4(tmp.d,tmp.d,tmp.d,np,n0,top);
766 bn_mul_mont_t4(tmp.d,tmp.d,tmp.d,np,n0,top);
767 bn_mul_mont_t4(tmp.d,tmp.d,tmp.d,np,n0,top);
768 bn_mul_mont_t4(tmp.d,tmp.d,tmp.d,np,n0,top);
769 bn_mul_mont_gather5_t4(tmp.d,tmp.d,powerbuf,np,n0,top,wvalue);
772 bn_flip_t4(tmp.d,tmp.d,top);
774 /* back to 32-bit domain */
776 bn_correct_top(&tmp);
777 OPENSSL_cleanse(np,top*sizeof(BN_ULONG));
781 #if defined(OPENSSL_BN_ASM_MONT5)
782 /* This optimization uses ideas from http://eprint.iacr.org/2011/239,
783 * specifically optimization of cache-timing attack countermeasures
784 * and pre-computation optimization. */
786 /* Dedicated window==4 case improves 512-bit RSA sign by ~15%, but as
787 * 512-bit RSA is hardly relevant, we omit it to spare size... */
790 void bn_mul_mont_gather5(BN_ULONG *rp,const BN_ULONG *ap,
791 const void *table,const BN_ULONG *np,
792 const BN_ULONG *n0,int num,int power);
793 void bn_scatter5(const BN_ULONG *inp,size_t num,
794 void *table,size_t power);
795 void bn_gather5(BN_ULONG *out,size_t num,
796 void *table,size_t power);
798 BN_ULONG *np=mont->N.d, *n0=mont->n0;
800 /* BN_to_montgomery can contaminate words above .top
801 * [in BN_DEBUG[_DEBUG] build]... */
802 for (i=am.top; i<top; i++) am.d[i]=0;
803 for (i=tmp.top; i<top; i++) tmp.d[i]=0;
805 bn_scatter5(tmp.d,top,powerbuf,0);
806 bn_scatter5(am.d,am.top,powerbuf,1);
807 bn_mul_mont(tmp.d,am.d,am.d,np,n0,top);
808 bn_scatter5(tmp.d,top,powerbuf,2);
813 /* Calculate a^i = a^(i-1) * a */
814 bn_mul_mont_gather5(tmp.d,am.d,powerbuf,np,n0,top,i-1);
815 bn_scatter5(tmp.d,top,powerbuf,i);
818 /* same as above, but uses squaring for 1/2 of operations */
819 for (i=4; i<32; i*=2)
821 bn_mul_mont(tmp.d,tmp.d,tmp.d,np,n0,top);
822 bn_scatter5(tmp.d,top,powerbuf,i);
827 bn_mul_mont_gather5(tmp.d,am.d,powerbuf,np,n0,top,i-1);
828 bn_scatter5(tmp.d,top,powerbuf,i);
829 for (j=2*i; j<32; j*=2)
831 bn_mul_mont(tmp.d,tmp.d,tmp.d,np,n0,top);
832 bn_scatter5(tmp.d,top,powerbuf,j);
837 bn_mul_mont_gather5(tmp.d,am.d,powerbuf,np,n0,top,i-1);
838 bn_scatter5(tmp.d,top,powerbuf,i);
839 bn_mul_mont(tmp.d,tmp.d,tmp.d,np,n0,top);
840 bn_scatter5(tmp.d,top,powerbuf,2*i);
844 bn_mul_mont_gather5(tmp.d,am.d,powerbuf,np,n0,top,i-1);
845 bn_scatter5(tmp.d,top,powerbuf,i);
849 for (wvalue=0, i=bits%5; i>=0; i--,bits--)
850 wvalue = (wvalue<<1)+BN_is_bit_set(p,bits);
851 bn_gather5(tmp.d,top,powerbuf,wvalue);
853 /* Scan the exponent one window at a time starting from the most
858 for (wvalue=0, i=0; i<5; i++,bits--)
859 wvalue = (wvalue<<1)+BN_is_bit_set(p,bits);
861 bn_mul_mont(tmp.d,tmp.d,tmp.d,np,n0,top);
862 bn_mul_mont(tmp.d,tmp.d,tmp.d,np,n0,top);
863 bn_mul_mont(tmp.d,tmp.d,tmp.d,np,n0,top);
864 bn_mul_mont(tmp.d,tmp.d,tmp.d,np,n0,top);
865 bn_mul_mont(tmp.d,tmp.d,tmp.d,np,n0,top);
866 bn_mul_mont_gather5(tmp.d,tmp.d,powerbuf,np,n0,top,wvalue);
870 bn_correct_top(&tmp);
875 if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&tmp, top, powerbuf, 0, numPowers)) goto err;
876 if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&am, top, powerbuf, 1, numPowers)) goto err;
878 /* If the window size is greater than 1, then calculate
879 * val[i=2..2^winsize-1]. Powers are computed as a*a^(i-1)
880 * (even powers could instead be computed as (a^(i/2))^2
881 * to use the slight performance advantage of sqr over mul).
885 if (!BN_mod_mul_montgomery(&tmp,&am,&am,mont,ctx)) goto err;
886 if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&tmp, top, powerbuf, 2, numPowers)) goto err;
887 for (i=3; i<numPowers; i++)
889 /* Calculate a^i = a^(i-1) * a */
890 if (!BN_mod_mul_montgomery(&tmp,&am,&tmp,mont,ctx))
892 if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&tmp, top, powerbuf, i, numPowers)) goto err;
897 for (wvalue=0, i=bits%window; i>=0; i--,bits--)
898 wvalue = (wvalue<<1)+BN_is_bit_set(p,bits);
899 if (!MOD_EXP_CTIME_COPY_FROM_PREBUF(&tmp,top,powerbuf,wvalue,numPowers)) goto err;
901 /* Scan the exponent one window at a time starting from the most
906 wvalue=0; /* The 'value' of the window */
908 /* Scan the window, squaring the result as we go */
909 for (i=0; i<window; i++,bits--)
911 if (!BN_mod_mul_montgomery(&tmp,&tmp,&tmp,mont,ctx)) goto err;
912 wvalue = (wvalue<<1)+BN_is_bit_set(p,bits);
915 /* Fetch the appropriate pre-computed value from the pre-buf */
916 if (!MOD_EXP_CTIME_COPY_FROM_PREBUF(&am, top, powerbuf, wvalue, numPowers)) goto err;
918 /* Multiply the result into the intermediate result */
919 if (!BN_mod_mul_montgomery(&tmp,&tmp,&am,mont,ctx)) goto err;
923 /* Convert the final result from montgomery to standard format */
924 if (!BN_from_montgomery(rr,&tmp,mont,ctx)) goto err;
927 if ((in_mont == NULL) && (mont != NULL)) BN_MONT_CTX_free(mont);
930 OPENSSL_cleanse(powerbuf,powerbufLen);
931 if (powerbufFree) OPENSSL_free(powerbufFree);
937 int BN_mod_exp_mont_word(BIGNUM *rr, BN_ULONG a, const BIGNUM *p,
938 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *in_mont)
940 BN_MONT_CTX *mont = NULL;
946 #define BN_MOD_MUL_WORD(r, w, m) \
947 (BN_mul_word(r, (w)) && \
948 (/* BN_ucmp(r, (m)) < 0 ? 1 :*/ \
949 (BN_mod(t, r, m, ctx) && (swap_tmp = r, r = t, t = swap_tmp, 1))))
950 /* BN_MOD_MUL_WORD is only used with 'w' large,
951 * so the BN_ucmp test is probably more overhead
952 * than always using BN_mod (which uses BN_copy if
953 * a similar test returns true). */
954 /* We can use BN_mod and do not need BN_nnmod because our
955 * accumulator is never negative (the result of BN_mod does
956 * not depend on the sign of the modulus).
958 #define BN_TO_MONTGOMERY_WORD(r, w, mont) \
959 (BN_set_word(r, (w)) && BN_to_montgomery(r, r, (mont), ctx))
961 if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0)
963 /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */
964 BNerr(BN_F_BN_MOD_EXP_MONT_WORD,ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
973 BNerr(BN_F_BN_MOD_EXP_MONT_WORD,BN_R_CALLED_WITH_EVEN_MODULUS);
977 a %= m->d[0]; /* make sure that 'a' is reduced */
979 bits = BN_num_bits(p);
996 if (d == NULL || r == NULL || t == NULL) goto err;
1002 if ((mont = BN_MONT_CTX_new()) == NULL) goto err;
1003 if (!BN_MONT_CTX_set(mont, m, ctx)) goto err;
1006 r_is_one = 1; /* except for Montgomery factor */
1010 /* The result is accumulated in the product r*w. */
1011 w = a; /* bit 'bits-1' of 'p' is always set */
1012 for (b = bits-2; b >= 0; b--)
1014 /* First, square r*w. */
1016 if ((next_w/w) != w) /* overflow */
1020 if (!BN_TO_MONTGOMERY_WORD(r, w, mont)) goto err;
1025 if (!BN_MOD_MUL_WORD(r, w, m)) goto err;
1032 if (!BN_mod_mul_montgomery(r, r, r, mont, ctx)) goto err;
1035 /* Second, multiply r*w by 'a' if exponent bit is set. */
1036 if (BN_is_bit_set(p, b))
1039 if ((next_w/a) != w) /* overflow */
1043 if (!BN_TO_MONTGOMERY_WORD(r, w, mont)) goto err;
1048 if (!BN_MOD_MUL_WORD(r, w, m)) goto err;
1056 /* Finally, set r:=r*w. */
1061 if (!BN_TO_MONTGOMERY_WORD(r, w, mont)) goto err;
1066 if (!BN_MOD_MUL_WORD(r, w, m)) goto err;
1070 if (r_is_one) /* can happen only if a == 1*/
1072 if (!BN_one(rr)) goto err;
1076 if (!BN_from_montgomery(rr, r, mont, ctx)) goto err;
1080 if ((in_mont == NULL) && (mont != NULL)) BN_MONT_CTX_free(mont);
1087 /* The old fallback, simple version :-) */
1088 int BN_mod_exp_simple(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
1089 const BIGNUM *m, BN_CTX *ctx)
1091 int i,j,bits,ret=0,wstart,wend,window,wvalue;
1094 /* Table of variables obtained from 'ctx' */
1095 BIGNUM *val[TABLE_SIZE];
1097 if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0)
1099 /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */
1100 BNerr(BN_F_BN_MOD_EXP_SIMPLE,ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
1104 bits=BN_num_bits(p);
1113 d = BN_CTX_get(ctx);
1114 val[0] = BN_CTX_get(ctx);
1115 if(!d || !val[0]) goto err;
1117 if (!BN_nnmod(val[0],a,m,ctx)) goto err; /* 1 */
1118 if (BN_is_zero(val[0]))
1125 window = BN_window_bits_for_exponent_size(bits);
1128 if (!BN_mod_mul(d,val[0],val[0],m,ctx))
1133 if(((val[i] = BN_CTX_get(ctx)) == NULL) ||
1134 !BN_mod_mul(val[i],val[i-1],d,m,ctx))
1139 start=1; /* This is used to avoid multiplication etc
1140 * when there is only the value '1' in the
1142 wvalue=0; /* The 'value' of the window */
1143 wstart=bits-1; /* The top bit of the window */
1144 wend=0; /* The bottom bit of the window */
1146 if (!BN_one(r)) goto err;
1150 if (BN_is_bit_set(p,wstart) == 0)
1153 if (!BN_mod_mul(r,r,r,m,ctx))
1155 if (wstart == 0) break;
1159 /* We now have wstart on a 'set' bit, we now need to work out
1160 * how bit a window to do. To do this we need to scan
1161 * forward until the last set bit before the end of the
1166 for (i=1; i<window; i++)
1168 if (wstart-i < 0) break;
1169 if (BN_is_bit_set(p,wstart-i))
1177 /* wend is the size of the current window */
1179 /* add the 'bytes above' */
1183 if (!BN_mod_mul(r,r,r,m,ctx))
1187 /* wvalue will be an odd number < 2^window */
1188 if (!BN_mod_mul(r,r,val[wvalue>>1],m,ctx))
1191 /* move the 'window' down further */
1195 if (wstart < 0) break;