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src/secp256k1/src/modinv64.h
- This file was added.
/*********************************************************************** | |||||
* Copyright (c) 2020 Peter Dettman * | |||||
* Distributed under the MIT software license, see the accompanying * | |||||
* file COPYING or https://www.opensource.org/licenses/mit-license.php.* | |||||
**********************************************************************/ | |||||
#ifndef SECP256K1_MODINV64_H | |||||
#define SECP256K1_MODINV64_H | |||||
#if defined HAVE_CONFIG_H | |||||
#include "libsecp256k1-config.h" | |||||
#endif | |||||
#include "util.h" | |||||
#ifndef SECP256K1_WIDEMUL_INT128 | |||||
#error "modinv64 requires 128-bit wide multiplication support" | |||||
#endif | |||||
/* A signed 62-bit limb representation of integers. | |||||
* | |||||
* Its value is sum(v[i] * 2^(62*i), i=0..4). */ | |||||
typedef struct { | |||||
int64_t v[5]; | |||||
} secp256k1_modinv64_signed62; | |||||
typedef struct { | |||||
/* The modulus in signed62 notation, must be odd and in [3, 2^256]. */ | |||||
secp256k1_modinv64_signed62 modulus; | |||||
/* modulus^{-1} mod 2^62 */ | |||||
uint64_t modulus_inv62; | |||||
} secp256k1_modinv64_modinfo; | |||||
/* Replace x with its modular inverse mod modinfo->modulus. x must be in range [0, modulus). | |||||
* If x is zero, the result will be zero as well. If not, the inverse must exist (i.e., the gcd of | |||||
* x and modulus must be 1). These rules are automatically satisfied if the modulus is prime. | |||||
* | |||||
* On output, all of x's limbs will be in [0, 2^62). | |||||
*/ | |||||
static void secp256k1_modinv64_var(secp256k1_modinv64_signed62 *x, const secp256k1_modinv64_modinfo *modinfo); | |||||
/* Same as secp256k1_modinv64_var, but constant time in x (not in the modulus). */ | |||||
static void secp256k1_modinv64(secp256k1_modinv64_signed62 *x, const secp256k1_modinv64_modinfo *modinfo); | |||||
#endif /* SECP256K1_MODINV64_H */ |