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https://github.com/openssl/openssl.git
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132 lines
2.6 KiB
C
132 lines
2.6 KiB
C
/*
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*
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* bn_modfs.c
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*
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* Some Modular Arithmetic Functions.
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*
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* Copyright (C) Lenka Fibikova 2000
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*
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*
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <assert.h>
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#include "bn_modfs.h"
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#define MAX_ROUNDS 10
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int BN_mod_sqrt(BIGNUM *x, BIGNUM *a, BIGNUM *p, BN_CTX *ctx)
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/* x^2 = a (mod p) */
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{
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int ret;
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BIGNUM *n0, *n1, *r, *b, *m;
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int max;
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assert(x != NULL && a != NULL && p != NULL && ctx != NULL);
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assert(BN_cmp(a, p) < 0);
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ret = BN_kronecker(a, p, ctx);
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if (ret < 0 || ret > 1) return 0;
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if (ret == 0)
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{
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if (!BN_zero(x)) return 0;
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return 1;
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}
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BN_CTX_start(ctx);
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n0 = BN_CTX_get(ctx);
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n1 = BN_CTX_get(ctx);
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if (n1 == NULL) goto err;
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if ((r = BN_new()) == NULL) goto err;
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if ((b = BN_new()) == NULL) goto err;
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if ((m = BN_new()) == NULL) goto err;
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if (!BN_zero(n0)) goto err;
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if (!BN_zero(n1)) goto err;
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if (!BN_zero(r)) goto err;
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if (!BN_zero(b)) goto err;
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if (!BN_zero(m)) goto err;
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max = 0;
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do
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{
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if (max++ > MAX_ROUNDS) goto err; /* if p is not prime could never stop*/
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if (!BN_add_word(m, 1)) goto err;
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ret = BN_kronecker(m, p, ctx);
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if (ret < -1 || ret > 1) goto err;
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}
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while (ret != -1);
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if (BN_copy(n1, p) == NULL) goto err;
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if (!BN_sub_word(n1, 1)) goto err;
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while (!BN_is_odd(n1))
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{
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if (!BN_add_word(r, 1)) goto err;
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if (!BN_rshift1(n1, n1)) goto err;
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}
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if (!BN_mod_exp_simple(n0, m, n1, p, ctx)) goto err;
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if (!BN_sub_word(n1, 1)) goto err;
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if (!BN_rshift1(n1, n1)) goto err;
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if (!BN_mod_exp_simple(x, a, n1, p, ctx)) goto err;
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if (!BN_mod_sqr(b, x, p, ctx)) goto err;
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if (!BN_mod_mul(b, b, a, p, ctx)) goto err;
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if (!BN_mod_mul(x, x, a, p, ctx)) goto err;
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while (!BN_is_one(b))
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{
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if (!BN_one(m)) goto err;
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if (!BN_mod_sqr(n1, b, p, ctx)) goto err;
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while(!BN_is_one(n1))
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{
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if (!BN_mod_mul(n1, n1, n1, p, ctx)) goto err;
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if (!BN_add_word(m, 1)) goto err;
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}
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if (!BN_sub(r, r, m)) goto err;
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if (!BN_sub_word(r, 1)) goto err;
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if (r->neg) goto err;
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if (BN_copy(n1, n0) == NULL) goto err;
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while(!BN_is_zero(r))
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{
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if (!BN_mod_mul(n1, n1, n1, p, ctx)) goto err;
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if (!BN_sub_word(r, 1)) goto err;
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}
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if (!BN_mod_mul(n0, n1, n1, p, ctx)) goto err;
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if (BN_copy(r, m) == NULL) goto err;
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if (!BN_mod_mul(x, x, n1, p, ctx)) goto err;
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if (!BN_mod_mul(b, b, n0, p, ctx)) goto err;
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}
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#ifdef TEST
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BN_mod_sqr(n0, x, p, ctx);
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if (BN_cmp(n0, a)) goto err;
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#endif
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if (r != NULL) BN_clear_free(r);
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if (b != NULL) BN_clear_free(b);
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if (m != NULL) BN_clear_free(m);
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BN_CTX_end(ctx);
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return 1;
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err:
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if (r != NULL) BN_clear_free(r);
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if (b != NULL) BN_clear_free(b);
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if (m != NULL) BN_clear_free(m);
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BN_CTX_end(ctx);
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return 0;
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}
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