field_5x52.h (2408B)
1 /*********************************************************************** 2 * Copyright (c) 2013, 2014 Pieter Wuille * 3 * Distributed under the MIT software license, see the accompanying * 4 * file COPYING or https://www.opensource.org/licenses/mit-license.php.* 5 ***********************************************************************/ 6 7 #ifndef SECP256K1_FIELD_REPR_H 8 #define SECP256K1_FIELD_REPR_H 9 10 #include <stdint.h> 11 12 /** This field implementation represents the value as 5 uint64_t limbs in base 13 * 2^52. */ 14 typedef struct { 15 /* A field element f represents the sum(i=0..4, f.n[i] << (i*52)) mod p, 16 * where p is the field modulus, 2^256 - 2^32 - 977. 17 * 18 * The individual limbs f.n[i] can exceed 2^52; the field's magnitude roughly 19 * corresponds to how much excess is allowed. The value 20 * sum(i=0..4, f.n[i] << (i*52)) may exceed p, unless the field element is 21 * normalized. */ 22 uint64_t n[5]; 23 /* 24 * Magnitude m requires: 25 * n[i] <= 2 * m * (2^52 - 1) for i=0..3 26 * n[4] <= 2 * m * (2^48 - 1) 27 * 28 * Normalized requires: 29 * n[i] <= (2^52 - 1) for i=0..3 30 * sum(i=0..4, n[i] << (i*52)) < p 31 * (together these imply n[4] <= 2^48 - 1) 32 */ 33 SECP256K1_FE_VERIFY_FIELDS 34 } haskellsecp256k1_v0_1_0_fe; 35 36 /* Unpacks a constant into a overlapping multi-limbed FE element. */ 37 #define SECP256K1_FE_CONST_INNER(d7, d6, d5, d4, d3, d2, d1, d0) { \ 38 (d0) | (((uint64_t)(d1) & 0xFFFFFUL) << 32), \ 39 ((uint64_t)(d1) >> 20) | (((uint64_t)(d2)) << 12) | (((uint64_t)(d3) & 0xFFUL) << 44), \ 40 ((uint64_t)(d3) >> 8) | (((uint64_t)(d4) & 0xFFFFFFFUL) << 24), \ 41 ((uint64_t)(d4) >> 28) | (((uint64_t)(d5)) << 4) | (((uint64_t)(d6) & 0xFFFFUL) << 36), \ 42 ((uint64_t)(d6) >> 16) | (((uint64_t)(d7)) << 16) \ 43 } 44 45 typedef struct { 46 uint64_t n[4]; 47 } haskellsecp256k1_v0_1_0_fe_storage; 48 49 #define SECP256K1_FE_STORAGE_CONST(d7, d6, d5, d4, d3, d2, d1, d0) {{ \ 50 (d0) | (((uint64_t)(d1)) << 32), \ 51 (d2) | (((uint64_t)(d3)) << 32), \ 52 (d4) | (((uint64_t)(d5)) << 32), \ 53 (d6) | (((uint64_t)(d7)) << 32) \ 54 }} 55 56 #define SECP256K1_FE_STORAGE_CONST_GET(d) \ 57 (uint32_t)(d.n[3] >> 32), (uint32_t)d.n[3], \ 58 (uint32_t)(d.n[2] >> 32), (uint32_t)d.n[2], \ 59 (uint32_t)(d.n[1] >> 32), (uint32_t)d.n[1], \ 60 (uint32_t)(d.n[0] >> 32), (uint32_t)d.n[0] 61 62 #endif /* SECP256K1_FIELD_REPR_H */