1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
|
/**********************************************************************
* Copyright (c) 2013-2015 Pieter Wuille *
* Distributed under the MIT software license, see the accompanying *
* file COPYING or http://www.opensource.org/licenses/mit-license.php.*
**********************************************************************/
#ifndef _SECP256K1_TESTRAND_IMPL_H_
#define _SECP256K1_TESTRAND_IMPL_H_
#include <stdint.h>
#include <string.h>
#include "testrand.h"
#include "hash.h"
static secp256k1_rfc6979_hmac_sha256_t secp256k1_test_rng;
static uint32_t secp256k1_test_rng_precomputed[8];
static int secp256k1_test_rng_precomputed_used = 8;
static uint64_t secp256k1_test_rng_integer;
static int secp256k1_test_rng_integer_bits_left = 0;
SECP256K1_INLINE static void secp256k1_rand_seed(const unsigned char *seed16) {
secp256k1_rfc6979_hmac_sha256_initialize(&secp256k1_test_rng, seed16, 16);
}
SECP256K1_INLINE static uint32_t secp256k1_rand32(void) {
if (secp256k1_test_rng_precomputed_used == 8) {
secp256k1_rfc6979_hmac_sha256_generate(&secp256k1_test_rng, (unsigned char*)(&secp256k1_test_rng_precomputed[0]), sizeof(secp256k1_test_rng_precomputed));
secp256k1_test_rng_precomputed_used = 0;
}
return secp256k1_test_rng_precomputed[secp256k1_test_rng_precomputed_used++];
}
static uint32_t secp256k1_rand_bits(int bits) {
uint32_t ret;
if (secp256k1_test_rng_integer_bits_left < bits) {
secp256k1_test_rng_integer |= (((uint64_t)secp256k1_rand32()) << secp256k1_test_rng_integer_bits_left);
secp256k1_test_rng_integer_bits_left += 32;
}
ret = secp256k1_test_rng_integer;
secp256k1_test_rng_integer >>= bits;
secp256k1_test_rng_integer_bits_left -= bits;
ret &= ((~((uint32_t)0)) >> (32 - bits));
return ret;
}
static uint32_t secp256k1_rand_int(uint32_t range) {
/* We want a uniform integer between 0 and range-1, inclusive.
* B is the smallest number such that range <= 2**B.
* two mechanisms implemented here:
* - generate B bits numbers until one below range is found, and return it
* - find the largest multiple M of range that is <= 2**(B+A), generate B+A
* bits numbers until one below M is found, and return it modulo range
* The second mechanism consumes A more bits of entropy in every iteration,
* but may need fewer iterations due to M being closer to 2**(B+A) then
* range is to 2**B. The array below (indexed by B) contains a 0 when the
* first mechanism is to be used, and the number A otherwise.
*/
static const int addbits[] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 2, 1, 0};
uint32_t trange, mult;
int bits = 0;
if (range <= 1) {
return 0;
}
trange = range - 1;
while (trange > 0) {
trange >>= 1;
bits++;
}
if (addbits[bits]) {
bits = bits + addbits[bits];
mult = ((~((uint32_t)0)) >> (32 - bits)) / range;
trange = range * mult;
} else {
trange = range;
mult = 1;
}
while(1) {
uint32_t x = secp256k1_rand_bits(bits);
if (x < trange) {
return (mult == 1) ? x : (x % range);
}
}
}
static void secp256k1_rand256(unsigned char *b32) {
secp256k1_rfc6979_hmac_sha256_generate(&secp256k1_test_rng, b32, 32);
}
static void secp256k1_rand_bytes_test(unsigned char *bytes, size_t len) {
size_t bits = 0;
memset(bytes, 0, len);
while (bits < len * 8) {
int now;
uint32_t val;
now = 1 + (secp256k1_rand_bits(6) * secp256k1_rand_bits(5) + 16) / 31;
val = secp256k1_rand_bits(1);
while (now > 0 && bits < len * 8) {
bytes[bits / 8] |= val << (bits % 8);
now--;
bits++;
}
}
}
static void secp256k1_rand256_test(unsigned char *b32) {
secp256k1_rand_bytes_test(b32, 32);
}
#endif
|
