diff options
Diffstat (limited to 'crypto/bn/bn_gcd.c')
| -rw-r--r-- | crypto/bn/bn_gcd.c | 203 |
1 files changed, 203 insertions, 0 deletions
diff --git a/crypto/bn/bn_gcd.c b/crypto/bn/bn_gcd.c new file mode 100644 index 0000000000..9b0bc2b100 --- /dev/null +++ b/crypto/bn/bn_gcd.c @@ -0,0 +1,203 @@ +/* crypto/bn/bn_gcd.c */ +/* Copyright (C) 1995-1997 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" + +#ifndef NOPROTO +static BIGNUM *euclid(BIGNUM *a, BIGNUM *b); +#else +static BIGNUM *euclid(); +#endif + +int BN_gcd(r,in_a,in_b,ctx) +BIGNUM *r,*in_a,*in_b; +BN_CTX *ctx; + { + BIGNUM *a,*b,*t; + int ret=0; + + a=ctx->bn[ctx->tos]; + b=ctx->bn[ctx->tos+1]; + + if (BN_copy(a,in_a) == NULL) goto err; + if (BN_copy(b,in_b) == NULL) goto err; + + if (BN_cmp(a,b) < 0) { t=a; a=b; b=t; } + t=euclid(a,b); + if (t == NULL) goto err; + + if (BN_copy(r,t) == NULL) goto err; + ret=1; +err: + return(ret); + } + +static BIGNUM *euclid(a,b) +BIGNUM *a,*b; + { + BIGNUM *t; + int shifts=0; + + for (;;) + { + if (BN_is_zero(b)) + break; + + if (BN_is_odd(a)) + { + if (BN_is_odd(b)) + { + if (!BN_sub(a,a,b)) goto err; + if (!BN_rshift1(a,a)) goto err; + if (BN_cmp(a,b) < 0) + { t=a; a=b; b=t; } + } + else /* a odd - b even */ + { + if (!BN_rshift1(b,b)) goto err; + if (BN_cmp(a,b) < 0) + { t=a; a=b; b=t; } + } + } + else /* a is even */ + { + if (BN_is_odd(b)) + { + if (!BN_rshift1(a,a)) goto err; + if (BN_cmp(a,b) < 0) + { t=a; a=b; b=t; } + } + else /* a even - b even */ + { + if (!BN_rshift1(a,a)) goto err; + if (!BN_rshift1(b,b)) goto err; + shifts++; + } + } + } + if (shifts) + { + if (!BN_lshift(a,a,shifts)) goto err; + } + return(a); +err: + return(NULL); + } + +/* solves ax == 1 (mod n) */ +BIGNUM *BN_mod_inverse(a, n, ctx) +BIGNUM *a; +BIGNUM *n; +BN_CTX *ctx; + { + BIGNUM *A,*B,*X,*Y,*M,*D,*R; + BIGNUM *ret=NULL,*T; + int sign; + + A=ctx->bn[ctx->tos]; + B=ctx->bn[ctx->tos+1]; + X=ctx->bn[ctx->tos+2]; + D=ctx->bn[ctx->tos+3]; + M=ctx->bn[ctx->tos+4]; + Y=ctx->bn[ctx->tos+5]; + ctx->tos+=6; + R=BN_new(); + if (R == NULL) goto err; + + BN_zero(X); + BN_one(Y); + if (BN_copy(A,a) == NULL) goto err; + if (BN_copy(B,n) == NULL) goto err; + sign=1; + + while (!BN_is_zero(B)) + { + if (!BN_div(D,M,A,B,ctx)) goto err; + T=A; + A=B; + B=M; + /* T has a struct, M does not */ + + if (!BN_mul(T,D,X)) goto err; + if (!BN_add(T,T,Y)) goto err; + M=Y; + Y=X; + X=T; + sign= -sign; + } + if (sign < 0) + { + if (!BN_sub(Y,n,Y)) goto err; + } + + if (BN_is_one(A)) + { if (!BN_mod(R,Y,n,ctx)) goto err; } + else + { + BNerr(BN_F_BN_MOD_INVERSE,BN_R_NO_INVERSE); + goto err; + } + ret=R; +err: + if ((ret == NULL) && (R != NULL)) BN_free(R); + ctx->tos-=6; + return(ret); + } + |