111 lines
3.9 KiB
C
111 lines
3.9 KiB
C
/**********************************************************************
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* Copyright (c) 2013-2015 Pieter Wuille *
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* Distributed under the MIT software license, see the accompanying *
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* file COPYING or http://www.opensource.org/licenses/mit-license.php.*
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**********************************************************************/
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#ifndef _SECP256K1_TESTRAND_IMPL_H_
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#define _SECP256K1_TESTRAND_IMPL_H_
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#include <stdint.h>
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#include <string.h>
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#include "testrand.h"
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#include "hash.h"
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static secp256k1_rfc6979_hmac_sha256_t secp256k1_test_rng;
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static uint32_t secp256k1_test_rng_precomputed[8];
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static int secp256k1_test_rng_precomputed_used = 8;
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static uint64_t secp256k1_test_rng_integer;
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static int secp256k1_test_rng_integer_bits_left = 0;
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SECP256K1_INLINE static void secp256k1_rand_seed(const unsigned char *seed16) {
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secp256k1_rfc6979_hmac_sha256_initialize(&secp256k1_test_rng, seed16, 16);
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}
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SECP256K1_INLINE static uint32_t secp256k1_rand32(void) {
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if (secp256k1_test_rng_precomputed_used == 8) {
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secp256k1_rfc6979_hmac_sha256_generate(&secp256k1_test_rng, (unsigned char*)(&secp256k1_test_rng_precomputed[0]), sizeof(secp256k1_test_rng_precomputed));
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secp256k1_test_rng_precomputed_used = 0;
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}
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return secp256k1_test_rng_precomputed[secp256k1_test_rng_precomputed_used++];
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}
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static uint32_t secp256k1_rand_bits(int bits) {
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uint32_t ret;
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if (secp256k1_test_rng_integer_bits_left < bits) {
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secp256k1_test_rng_integer |= (((uint64_t)secp256k1_rand32()) << secp256k1_test_rng_integer_bits_left);
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secp256k1_test_rng_integer_bits_left += 32;
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}
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ret = secp256k1_test_rng_integer;
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secp256k1_test_rng_integer >>= bits;
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secp256k1_test_rng_integer_bits_left -= bits;
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ret &= ((~((uint32_t)0)) >> (32 - bits));
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return ret;
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}
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static uint32_t secp256k1_rand_int(uint32_t range) {
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/* We want a uniform integer between 0 and range-1, inclusive.
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* B is the smallest number such that range <= 2**B.
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* two mechanisms implemented here:
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* - generate B bits numbers until one below range is found, and return it
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* - find the largest multiple M of range that is <= 2**(B+A), generate B+A
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* bits numbers until one below M is found, and return it modulo range
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* The second mechanism consumes A more bits of entropy in every iteration,
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* but may need fewer iterations due to M being closer to 2**(B+A) then
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* range is to 2**B. The array below (indexed by B) contains a 0 when the
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* first mechanism is to be used, and the number A otherwise.
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*/
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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};
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uint32_t trange, mult;
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int bits = 0;
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if (range <= 1) {
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return 0;
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}
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trange = range - 1;
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while (trange > 0) {
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trange >>= 1;
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bits++;
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}
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if (addbits[bits]) {
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bits = bits + addbits[bits];
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mult = ((~((uint32_t)0)) >> (32 - bits)) / range;
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trange = range * mult;
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} else {
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trange = range;
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mult = 1;
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}
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while(1) {
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uint32_t x = secp256k1_rand_bits(bits);
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if (x < trange) {
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return (mult == 1) ? x : (x % range);
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}
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}
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}
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static void secp256k1_rand256(unsigned char *b32) {
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secp256k1_rfc6979_hmac_sha256_generate(&secp256k1_test_rng, b32, 32);
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}
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static void secp256k1_rand_bytes_test(unsigned char *bytes, size_t len) {
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size_t bits = 0;
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memset(bytes, 0, len);
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while (bits < len * 8) {
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int now;
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uint32_t val;
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now = 1 + (secp256k1_rand_bits(6) * secp256k1_rand_bits(5) + 16) / 31;
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val = secp256k1_rand_bits(1);
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while (now > 0 && bits < len * 8) {
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bytes[bits / 8] |= val << (bits % 8);
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now--;
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bits++;
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}
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}
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}
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static void secp256k1_rand256_test(unsigned char *b32) {
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secp256k1_rand_bytes_test(b32, 32);
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}
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#endif
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