43 lines
1.6 KiB
C
43 lines
1.6 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_MODINV32_H
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#define SECP256K1_MODINV32_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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/* A signed 30-bit limb representation of integers.
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*
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* Its value is sum(v[i] * 2^(30*i), i=0..8). */
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typedef struct {
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int32_t v[9];
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} secp256k1_modinv32_signed30;
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typedef struct {
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/* The modulus in signed30 notation, must be odd and in [3, 2^256]. */
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secp256k1_modinv32_signed30 modulus;
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/* modulus^{-1} mod 2^30 */
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uint32_t modulus_inv30;
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} secp256k1_modinv32_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, 2^30).
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*/
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static void secp256k1_modinv32_var(secp256k1_modinv32_signed30 *x, const secp256k1_modinv32_modinfo *modinfo);
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/* Same as secp256k1_modinv32_var, but constant time in x (not in the modulus). */
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static void secp256k1_modinv32(secp256k1_modinv32_signed30 *x, const secp256k1_modinv32_modinfo *modinfo);
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#endif /* SECP256K1_MODINV32_H */
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