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Improve testrand: add extra random functions 

This commit adds functions:
* secp256k1_rand_bits, which works like secp256k1_rand32, but consumes
  less randomness
* secp256k1_rand_int, which produces a uniform integer over any range
* secp256k1_rand_bytes_test, which works like secp256k1_rand256_test
  but for arbitrary byte array
This commit is contained in:
Pieter Wuille 2015-10-17 20:56:53 +02:00
parent 31994c8e5b
commit 251b1a62d3
2 changed files with 57 additions and 18 deletions
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12
src/testrand.h
View File

@ -16,13 +16,23 @@
/** Seed the pseudorandom number generator for testing. */
SECP256K1_INLINE static void secp256k1_rand_seed(const unsigned char *seed16);
/** Generate a pseudorandom 32-bit number. */
/** Generate a pseudorandom number in the range [0..2**32-1]. */
static uint32_t secp256k1_rand32(void);
/** Generate a pseudorandom number in the range [0..2**bits-1]. Bits must be 1 or
* more. */
static uint32_t secp256k1_rand_bits(int bits);
/** Generate a pseudorandom number in the range [0..range-1]. */
static uint32_t secp256k1_rand_int(uint32_t range);
/** Generate a pseudorandom 32-byte array. */
static void secp256k1_rand256(unsigned char *b32);
/** Generate a pseudorandom 32-byte array with long sequences of zero and one bits. */
static void secp256k1_rand256_test(unsigned char *b32);
/** Generate pseudorandom bytes with long sequences of zero and one bits. */
static void secp256k1_rand_bytes_test(unsigned char *bytes, size_t len);
#endif

63
src/testrand_impl.h
View File

@ -1,5 +1,5 @@
/**********************************************************************
* Copyright (c) 2013, 2014 Pieter Wuille *
* 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.*
**********************************************************************/
@ -16,6 +16,8 @@
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);
@ -29,32 +31,59 @@ SECP256K1_INLINE static uint32_t secp256k1_rand32(void) {
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) {
int bits = 0;
uint32_t ret = range - 1;
if (range <= 1) {
return 0;
}
while (ret > 0) {
ret >>= 1;
bits++;
}
while (1) {
ret = secp256k1_rand_bits(bits);
if (ret < range) {
return ret;
}
}
}
static void secp256k1_rand256(unsigned char *b32) {
secp256k1_rfc6979_hmac_sha256_generate(&secp256k1_test_rng, b32, 32);
}
static void secp256k1_rand256_test(unsigned char *b32) {
int bits=0;
uint64_t ent = 0;
int entleft = 0;
memset(b32, 0, 32);
while (bits < 256) {
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;
if (entleft < 12) {
ent |= ((uint64_t)secp256k1_rand32()) << entleft;
entleft += 32;
}
now = 1 + ((ent % 64)*((ent >> 6) % 32)+16)/31;
val = 1 & (ent >> 11);
ent >>= 12;
entleft -= 12;
while (now > 0 && bits < 256) {
b32[bits / 8] |= val << (bits % 8);
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