Bitcoin Core  27.99.0 P2P Digital Currency
field_10x26.h
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1 /***********************************************************************
2  * Copyright (c) 2013, 2014 Pieter Wuille *
3  * Distributed under the MIT software license, see the accompanying *
5  ***********************************************************************/
6
7 #ifndef SECP256K1_FIELD_REPR_H
8 #define SECP256K1_FIELD_REPR_H
9
10 #include <stdint.h>
11
14 typedef struct {
15  /* A field element f represents the sum(i=0..9, f.n[i] << (i*26)) mod p,
16  * where p is the field modulus, 2^256 - 2^32 - 977.
17  *
18  * The individual limbs f.n[i] can exceed 2^26; the field's magnitude roughly
19  * corresponds to how much excess is allowed. The value
20  * sum(i=0..9, f.n[i] << (i*26)) may exceed p, unless the field element is
21  * normalized. */
22  uint32_t n[10];
23  /*
24  * Magnitude m requires:
25  * n[i] <= 2 * m * (2^26 - 1) for i=0..8
26  * n[9] <= 2 * m * (2^22 - 1)
27  *
28  * Normalized requires:
29  * n[i] <= (2^26 - 1) for i=0..8
30  * sum(i=0..9, n[i] << (i*26)) < p
31  * (together these imply n[9] <= 2^22 - 1)
32  */
34 } secp256k1_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) & 0x3FFFFFFUL, \
39  (((uint32_t)d0) >> 26) | (((uint32_t)(d1) & 0xFFFFFUL) << 6), \
40  (((uint32_t)d1) >> 20) | (((uint32_t)(d2) & 0x3FFFUL) << 12), \
41  (((uint32_t)d2) >> 14) | (((uint32_t)(d3) & 0xFFUL) << 18), \
42  (((uint32_t)d3) >> 8) | (((uint32_t)(d4) & 0x3UL) << 24), \
43  (((uint32_t)d4) >> 2) & 0x3FFFFFFUL, \
44  (((uint32_t)d4) >> 28) | (((uint32_t)(d5) & 0x3FFFFFUL) << 4), \
45  (((uint32_t)d5) >> 22) | (((uint32_t)(d6) & 0xFFFFUL) << 10), \
46  (((uint32_t)d6) >> 16) | (((uint32_t)(d7) & 0x3FFUL) << 16), \
47  (((uint32_t)d7) >> 10) \
48 }
49
50 typedef struct {
51  uint32_t n[8];
53
54 #define SECP256K1_FE_STORAGE_CONST(d7, d6, d5, d4, d3, d2, d1, d0) {{ (d0), (d1), (d2), (d3), (d4), (d5), (d6), (d7) }}
55 #define SECP256K1_FE_STORAGE_CONST_GET(d) d.n[7], d.n[6], d.n[5], d.n[4],d.n[3], d.n[2], d.n[1], d.n[0]
56
57 #endif /* SECP256K1_FIELD_REPR_H */
#define SECP256K1_FE_VERIFY_FIELDS
Definition: field.h:37
This field implementation represents the value as 10 uint32_t limbs in base 2^26.
Definition: field_10x26.h:14