47 lines
1.8 KiB
C
47 lines
1.8 KiB
C
/***********************************************************************
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* Copyright (c) 2020 Peter Dettman *
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* Distributed under the MIT software license, see the accompanying *
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* file COPYING or https://www.opensource.org/licenses/mit-license.php.*
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**********************************************************************/
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#ifndef SECP256K1_MODINV64_H
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#define SECP256K1_MODINV64_H
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#if defined HAVE_CONFIG_H
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#include "libsecp256k1-config.h"
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#endif
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#include "util.h"
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#ifndef SECP256K1_WIDEMUL_INT128
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#error "modinv64 requires 128-bit wide multiplication support"
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#endif
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/* A signed 62-bit limb representation of integers.
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*
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* Its value is sum(v[i] * 2^(62*i), i=0..4). */
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typedef struct {
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int64_t v[5];
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} rustsecp256k1_v0_5_0_modinv64_signed62;
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typedef struct {
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/* The modulus in signed62 notation, must be odd and in [3, 2^256]. */
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rustsecp256k1_v0_5_0_modinv64_signed62 modulus;
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/* modulus^{-1} mod 2^62 */
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uint64_t modulus_inv62;
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} rustsecp256k1_v0_5_0_modinv64_modinfo;
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/* Replace x with its modular inverse mod modinfo->modulus. x must be in range [0, modulus).
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* If x is zero, the result will be zero as well. If not, the inverse must exist (i.e., the gcd of
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* x and modulus must be 1). These rules are automatically satisfied if the modulus is prime.
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*
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* On output, all of x's limbs will be in [0, 2^62).
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*/
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static void rustsecp256k1_v0_5_0_modinv64_var(rustsecp256k1_v0_5_0_modinv64_signed62 *x, const rustsecp256k1_v0_5_0_modinv64_modinfo *modinfo);
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/* Same as rustsecp256k1_v0_5_0_modinv64_var, but constant time in x (not in the modulus). */
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static void rustsecp256k1_v0_5_0_modinv64(rustsecp256k1_v0_5_0_modinv64_signed62 *x, const rustsecp256k1_v0_5_0_modinv64_modinfo *modinfo);
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#endif /* SECP256K1_MODINV64_H */
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