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/***********************************************************************
* Copyright (c) 2013-2015 Pieter Wuille *
* Distributed under the MIT software license, see the accompanying *
* file COPYING or https://www.opensource.org/licenses/mit-license.php.*
***********************************************************************/
#ifndef SECP256K1_TESTRAND_IMPL_H
#define SECP256K1_TESTRAND_IMPL_H
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include "testrand.h"
#include "hash.h"
static secp256k1_rfc6979_hmac_sha256 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_testrand_seed(const unsigned char *seed16) {
secp256k1_rfc6979_hmac_sha256_initialize(&secp256k1_test_rng, seed16, 16);
}
SECP256K1_INLINE static uint32_t secp256k1_testrand32(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_testrand_bits(int bits) {
uint32_t ret;
if (secp256k1_test_rng_integer_bits_left < bits) {
secp256k1_test_rng_integer |= (((uint64_t)secp256k1_testrand32()) << 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_testrand_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_testrand_bits(bits);
if (x < trange) {
return (mult == 1) ? x : (x % range);
}
}
}
static void secp256k1_testrand256(unsigned char *b32) {
secp256k1_rfc6979_hmac_sha256_generate(&secp256k1_test_rng, b32, 32);
}
static void secp256k1_testrand_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_testrand_bits(6) * secp256k1_testrand_bits(5) + 16) / 31;
val = secp256k1_testrand_bits(1);
while (now > 0 && bits < len * 8) {
bytes[bits / 8] |= val << (bits % 8);
now--;
bits++;
}
}
}
static void secp256k1_testrand256_test(unsigned char *b32) {
secp256k1_testrand_bytes_test(b32, 32);
}
static void secp256k1_testrand_flip(unsigned char *b, size_t len) {
b[secp256k1_testrand_int(len)] ^= (1 << secp256k1_testrand_int(8));
}
static void secp256k1_testrand_init(const char* hexseed) {
unsigned char seed16[16] = {0};
if (hexseed && strlen(hexseed) != 0) {
int pos = 0;
while (pos < 16 && hexseed[0] != 0 && hexseed[1] != 0) {
unsigned short sh;
if ((sscanf(hexseed, "%2hx", &sh)) == 1) {
seed16[pos] = sh;
} else {
break;
}
hexseed += 2;
pos++;
}
} else {
FILE *frand = fopen("/dev/urandom", "r");
if ((frand == NULL) || fread(&seed16, 1, sizeof(seed16), frand) != sizeof(seed16)) {
uint64_t t = time(NULL) * (uint64_t)1337;
fprintf(stderr, "WARNING: could not read 16 bytes from /dev/urandom; falling back to insecure PRNG\n");
seed16[0] ^= t;
seed16[1] ^= t >> 8;
seed16[2] ^= t >> 16;
seed16[3] ^= t >> 24;
seed16[4] ^= t >> 32;
seed16[5] ^= t >> 40;
seed16[6] ^= t >> 48;
seed16[7] ^= t >> 56;
}
if (frand) {
fclose(frand);
}
}
printf("random seed = %02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x\n", seed16[0], seed16[1], seed16[2], seed16[3], seed16[4], seed16[5], seed16[6], seed16[7], seed16[8], seed16[9], seed16[10], seed16[11], seed16[12], seed16[13], seed16[14], seed16[15]);
secp256k1_testrand_seed(seed16);
}
static void secp256k1_testrand_finish(void) {
unsigned char run32[32];
secp256k1_testrand256(run32);
printf("random run = %02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x\n", run32[0], run32[1], run32[2], run32[3], run32[4], run32[5], run32[6], run32[7], run32[8], run32[9], run32[10], run32[11], run32[12], run32[13], run32[14], run32[15]);
}
#endif /* SECP256K1_TESTRAND_IMPL_H */
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