Bitcoin Core  27.99.0 P2P Digital Currency
modinv64.h
Go to the documentation of this file.
1 /***********************************************************************
2  * Copyright (c) 2020 Peter Dettman *
5  **********************************************************************/
6
7 #ifndef SECP256K1_MODINV64_H
8 #define SECP256K1_MODINV64_H
9
10 #include "util.h"
11
12 #ifndef SECP256K1_WIDEMUL_INT128
13 #error "modinv64 requires 128-bit wide multiplication support"
14 #endif
15
16 /* A signed 62-bit limb representation of integers.
17  *
18  * Its value is sum(v[i] * 2^(62*i), i=0..4). */
19 typedef struct {
20  int64_t v[5];
22
23 typedef struct {
24  /* The modulus in signed62 notation, must be odd and in [3, 2^256]. */
26
27  /* modulus^{-1} mod 2^62 */
28  uint64_t modulus_inv62;
30
31 /* Replace x with its modular inverse mod modinfo->modulus. x must be in range [0, modulus).
32  * If x is zero, the result will be zero as well. If not, the inverse must exist (i.e., the gcd of
33  * x and modulus must be 1). These rules are automatically satisfied if the modulus is prime.
34  *
35  * On output, all of x's limbs will be in [0, 2^62).
36  */
38
39 /* Same as secp256k1_modinv64_var, but constant time in x (not in the modulus). */
41
42 /* Compute the Jacobi symbol for (x | modinfo->modulus). x must be coprime with modulus (and thus
43  * cannot be 0, as modulus >= 3). All limbs of x must be non-negative. Returns 0 if the result
44  * cannot be computed. */
46
47 #endif /* SECP256K1_MODINV64_H */
static void secp256k1_modinv64(secp256k1_modinv64_signed62 *x, const secp256k1_modinv64_modinfo *modinfo)
static void secp256k1_modinv64_var(secp256k1_modinv64_signed62 *x, const secp256k1_modinv64_modinfo *modinfo)
static int secp256k1_jacobi64_maybe_var(const secp256k1_modinv64_signed62 *x, const secp256k1_modinv64_modinfo *modinfo)
secp256k1_modinv64_signed62 modulus
Definition: modinv64.h:25