EC_GROUP *EC_GROUP_new_curve_GFp(const BIGNUM *p, const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx) { const EC_METHOD *meth; EC_GROUP *ret; meth = EC_GFp_nist_method(); ret = EC_GROUP_new(meth); if (ret == NULL) return NULL; if (!EC_GROUP_set_curve_GFp(ret, p, a, b, ctx)) { unsigned long err; err = ERR_peek_last_error(); if (!(ERR_GET_LIB(err) == ERR_LIB_EC && ((ERR_GET_REASON(err) == EC_R_NOT_A_NIST_PRIME) || (ERR_GET_REASON(err) == EC_R_NOT_A_SUPPORTED_NIST_PRIME)))) { /* real error */ EC_GROUP_clear_free(ret); return NULL; } /* not an actual error, we just cannot use EC_GFp_nist_method */ ERR_clear_error(); EC_GROUP_clear_free(ret); meth = EC_GFp_mont_method(); ret = EC_GROUP_new(meth); if (ret == NULL) return NULL; if (!EC_GROUP_set_curve_GFp(ret, p, a, b, ctx)) { EC_GROUP_clear_free(ret); return NULL; } } return ret; }
EC_GROUP *EC_GROUP_new_curve_GFp(const BIGNUM *p, const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx) { const EC_METHOD *meth; EC_GROUP *ret; #if defined(OPENSSL_BN_ASM_MONT) /* * This might appear controversial, but the fact is that generic * prime method was observed to deliver better performance even * for NIST primes on a range of platforms, e.g.: 60%-15% * improvement on IA-64, ~25% on ARM, 30%-90% on P4, 20%-25% * in 32-bit build and 35%--12% in 64-bit build on Core2... * Coefficients are relative to optimized bn_nist.c for most * intensive ECDSA verify and ECDH operations for 192- and 521- * bit keys respectively. Choice of these boundary values is * arguable, because the dependency of improvement coefficient * from key length is not a "monotone" curve. For example while * 571-bit result is 23% on ARM, 384-bit one is -1%. But it's * generally faster, sometimes "respectfully" faster, sometimes * "tolerably" slower... What effectively happens is that loop * with bn_mul_add_words is put against bn_mul_mont, and the * latter "wins" on short vectors. Correct solution should be * implementing dedicated NxN multiplication subroutines for * small N. But till it materializes, let's stick to generic * prime method... * <appro> */ meth = EC_GFp_mont_method(); #else if (BN_nist_mod_func(p)) meth = EC_GFp_nist_method(); else meth = EC_GFp_mont_method(); #endif ret = EC_GROUP_new(meth); if (ret == NULL) return NULL; if (!EC_GROUP_set_curve(ret, p, a, b, ctx)) { EC_GROUP_clear_free(ret); return NULL; } return ret; }