| /* crypto/bn/bn_recp.c */ |
| /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) |
| * All rights reserved. |
| * |
| * This package is an SSL implementation written |
| * by Eric Young (eay@cryptsoft.com). |
| * The implementation was written so as to conform with Netscapes SSL. |
| * |
| * This library is free for commercial and non-commercial use as long as |
| * the following conditions are aheared to. The following conditions |
| * apply to all code found in this distribution, be it the RC4, RSA, |
| * lhash, DES, etc., code; not just the SSL code. The SSL documentation |
| * included with this distribution is covered by the same copyright terms |
| * except that the holder is Tim Hudson (tjh@cryptsoft.com). |
| * |
| * Copyright remains Eric Young's, and as such any Copyright notices in |
| * the code are not to be removed. |
| * If this package is used in a product, Eric Young should be given attribution |
| * as the author of the parts of the library used. |
| * This can be in the form of a textual message at program startup or |
| * in documentation (online or textual) provided with the package. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * 1. Redistributions of source code must retain the copyright |
| * notice, this list of conditions and the following disclaimer. |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * 3. All advertising materials mentioning features or use of this software |
| * must display the following acknowledgement: |
| * "This product includes cryptographic software written by |
| * Eric Young (eay@cryptsoft.com)" |
| * The word 'cryptographic' can be left out if the rouines from the library |
| * being used are not cryptographic related :-). |
| * 4. If you include any Windows specific code (or a derivative thereof) from |
| * the apps directory (application code) you must include an acknowledgement: |
| * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)" |
| * |
| * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND |
| * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE |
| * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
| * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
| * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| * SUCH DAMAGE. |
| * |
| * The licence and distribution terms for any publically available version or |
| * derivative of this code cannot be changed. i.e. this code cannot simply be |
| * copied and put under another distribution licence |
| * [including the GNU Public Licence.] |
| */ |
| |
| #include <stdio.h> |
| #include "cryptlib.h" |
| #include "bn_lcl.h" |
| |
| void BN_RECP_CTX_init(BN_RECP_CTX *recp) |
| { |
| BN_init(&(recp->N)); |
| BN_init(&(recp->Nr)); |
| recp->num_bits=0; |
| recp->flags=0; |
| } |
| |
| BN_RECP_CTX *BN_RECP_CTX_new(void) |
| { |
| BN_RECP_CTX *ret; |
| |
| if ((ret=(BN_RECP_CTX *)OPENSSL_malloc(sizeof(BN_RECP_CTX))) == NULL) |
| return(NULL); |
| |
| BN_RECP_CTX_init(ret); |
| ret->flags=BN_FLG_MALLOCED; |
| return(ret); |
| } |
| |
| void BN_RECP_CTX_free(BN_RECP_CTX *recp) |
| { |
| if(recp == NULL) |
| return; |
| |
| BN_free(&(recp->N)); |
| BN_free(&(recp->Nr)); |
| if (recp->flags & BN_FLG_MALLOCED) |
| OPENSSL_free(recp); |
| } |
| |
| int BN_RECP_CTX_set(BN_RECP_CTX *recp, const BIGNUM *d, BN_CTX *ctx) |
| { |
| if (!BN_copy(&(recp->N),d)) return 0; |
| BN_zero(&(recp->Nr)); |
| recp->num_bits=BN_num_bits(d); |
| recp->shift=0; |
| return(1); |
| } |
| |
| int BN_mod_mul_reciprocal(BIGNUM *r, const BIGNUM *x, const BIGNUM *y, |
| BN_RECP_CTX *recp, BN_CTX *ctx) |
| { |
| int ret=0; |
| BIGNUM *a; |
| const BIGNUM *ca; |
| |
| BN_CTX_start(ctx); |
| if ((a = BN_CTX_get(ctx)) == NULL) goto err; |
| if (y != NULL) |
| { |
| if (x == y) |
| { if (!BN_sqr(a,x,ctx)) goto err; } |
| else |
| { if (!BN_mul(a,x,y,ctx)) goto err; } |
| ca = a; |
| } |
| else |
| ca=x; /* Just do the mod */ |
| |
| ret = BN_div_recp(NULL,r,ca,recp,ctx); |
| err: |
| BN_CTX_end(ctx); |
| bn_check_top(r); |
| return(ret); |
| } |
| |
| int BN_div_recp(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m, |
| BN_RECP_CTX *recp, BN_CTX *ctx) |
| { |
| int i,j,ret=0; |
| BIGNUM *a,*b,*d,*r; |
| |
| BN_CTX_start(ctx); |
| a=BN_CTX_get(ctx); |
| b=BN_CTX_get(ctx); |
| if (dv != NULL) |
| d=dv; |
| else |
| d=BN_CTX_get(ctx); |
| if (rem != NULL) |
| r=rem; |
| else |
| r=BN_CTX_get(ctx); |
| if (a == NULL || b == NULL || d == NULL || r == NULL) goto err; |
| |
| if (BN_ucmp(m,&(recp->N)) < 0) |
| { |
| BN_zero(d); |
| if (!BN_copy(r,m)) return 0; |
| BN_CTX_end(ctx); |
| return(1); |
| } |
| |
| /* We want the remainder |
| * Given input of ABCDEF / ab |
| * we need multiply ABCDEF by 3 digests of the reciprocal of ab |
| * |
| */ |
| |
| /* i := max(BN_num_bits(m), 2*BN_num_bits(N)) */ |
| i=BN_num_bits(m); |
| j=recp->num_bits<<1; |
| if (j>i) i=j; |
| |
| /* Nr := round(2^i / N) */ |
| if (i != recp->shift) |
| recp->shift=BN_reciprocal(&(recp->Nr),&(recp->N), |
| i,ctx); /* BN_reciprocal returns i, or -1 for an error */ |
| if (recp->shift == -1) goto err; |
| |
| /* d := |round(round(m / 2^BN_num_bits(N)) * recp->Nr / 2^(i - BN_num_bits(N)))| |
| * = |round(round(m / 2^BN_num_bits(N)) * round(2^i / N) / 2^(i - BN_num_bits(N)))| |
| * <= |(m / 2^BN_num_bits(N)) * (2^i / N) * (2^BN_num_bits(N) / 2^i)| |
| * = |m/N| |
| */ |
| if (!BN_rshift(a,m,recp->num_bits)) goto err; |
| if (!BN_mul(b,a,&(recp->Nr),ctx)) goto err; |
| if (!BN_rshift(d,b,i-recp->num_bits)) goto err; |
| d->neg=0; |
| |
| if (!BN_mul(b,&(recp->N),d,ctx)) goto err; |
| if (!BN_usub(r,m,b)) goto err; |
| r->neg=0; |
| |
| #if 1 |
| j=0; |
| while (BN_ucmp(r,&(recp->N)) >= 0) |
| { |
| if (j++ > 2) |
| { |
| BNerr(BN_F_BN_DIV_RECP,BN_R_BAD_RECIPROCAL); |
| goto err; |
| } |
| if (!BN_usub(r,r,&(recp->N))) goto err; |
| if (!BN_add_word(d,1)) goto err; |
| } |
| #endif |
| |
| r->neg=BN_is_zero(r)?0:m->neg; |
| d->neg=m->neg^recp->N.neg; |
| ret=1; |
| err: |
| BN_CTX_end(ctx); |
| bn_check_top(dv); |
| bn_check_top(rem); |
| return(ret); |
| } |
| |
| /* len is the expected size of the result |
| * We actually calculate with an extra word of precision, so |
| * we can do faster division if the remainder is not required. |
| */ |
| /* r := 2^len / m */ |
| int BN_reciprocal(BIGNUM *r, const BIGNUM *m, int len, BN_CTX *ctx) |
| { |
| int ret= -1; |
| BIGNUM *t; |
| |
| BN_CTX_start(ctx); |
| if((t = BN_CTX_get(ctx)) == NULL) goto err; |
| |
| if (!BN_set_bit(t,len)) goto err; |
| |
| if (!BN_div(r,NULL,t,m,ctx)) goto err; |
| |
| ret=len; |
| err: |
| bn_check_top(r); |
| BN_CTX_end(ctx); |
| return(ret); |
| } |