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Use MGF1 with SHA-512 as BLISS random oracle

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This commit is contained in:
Andreas Steffen
2015-07-27 22:09:08 +02:00
parent 7b7c510eec
commit e57190c312
5 changed files with 65 additions and 74 deletions
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src/libstrongswan/plugins/bliss/bliss_utils.c
+43 -44
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@@ -17,6 +17,7 @@
#include <asn1/asn1.h>
#include <crypto/hashers/hasher.h>
#include <crypto/mgf1/mgf1_bitspender.h>
#include <utils/debug.h>
/**
@@ -54,64 +55,62 @@ void bliss_utils_round_and_drop(bliss_param_set_t *set, int32_t *x, int16_t *xd)
/**
* See header.
*/
bool bliss_utils_generate_c(hasher_t *hasher, chunk_t data_hash, uint16_t *ud,
int n, uint16_t kappa, uint16_t *c_indices)
bool bliss_utils_generate_c(hash_algorithm_t alg, chunk_t data_hash,
uint16_t *ud, bliss_param_set_t *set,
uint16_t *c_indices)
{
int i, index_found, rounds;
uint16_t index;
uint8_t hash[HASH_SIZE_SHA512], un16_buf[2];
chunk_t un16 = { un16_buf, 2 };
bool index_taken[n];
int i, index_trials = 0, index_found = 0;
bool index_taken[set->n];
uint32_t index;
uint8_t *seed_pos;
chunk_t seed;
mgf1_bitspender_t *bitspender;
for (i = 0; i < n; i++)
seed = chunk_alloca(data_hash.len + set->n * sizeof(uint16_t));
/* the data hash makes up the first part of the oracle seed */
memcpy(seed.ptr, data_hash.ptr, data_hash.len);
seed_pos = seed.ptr + data_hash.len;
/* followed by the n elements of the ud vector in network order */
for (i = 0; i < set->n; i++)
{
htoun16(seed_pos, ud[i]);
seed_pos += sizeof(uint16_t);
}
bitspender = mgf1_bitspender_create(alg, seed, FALSE);
if (!bitspender)
{
return NULL;
}
for (i = 0; i < set->n; i++)
{
index_taken[i] = FALSE;
}
index_found = 0;
for (rounds = 0; rounds < 0x10000; rounds++)
DBG3(DBG_LIB, " i c_index[i]");
while (bitspender->get_bits(bitspender, set->n_bits, &index))
{
/* hash data */
if (!hasher->get_hash(hasher, data_hash, NULL))
{
return FALSE;
}
index_trials++;
/* followed by the ud vector */
for (i = 0; i < n; i++)
if (!index_taken[index])
{
htoun16(un16_buf, ud[i]);
if (!hasher->get_hash(hasher, un16, NULL))
DBG3(DBG_LIB, "%2u %8u", index_found, index);
c_indices[index_found++] = index;
index_taken[index] = TRUE;
if (index_found == set->kappa)
{
return FALSE;
}
}
/* hash the round iteration */
htoun16(un16_buf, rounds);
if (!hasher->get_hash(hasher, un16, hash))
{
return FALSE;
}
for (i = 0; i < HASH_SIZE_SHA512; i += 2)
{
index = untoh16(&hash[i]) % n;
if (!index_taken[index])
{
c_indices[index_found++] = index;
index_taken[index] = TRUE;
if (index_found == kappa)
{
return TRUE;
}
DBG3(DBG_LIB, "%2d index trials", index_trials);
bitspender->destroy(bitspender);
return TRUE;
}
}
}
DBG1(DBG_LIB, "aborted c_indices generation after 2^16 rounds");
bitspender->destroy(bitspender);
return FALSE;
}