/*!
* Hash a null-terminated string to a byte array.
*
* @param input_buf The input buffer.
* @param input_len The input buffer length (in bytes).
* @param output_buf A pre-allocated output buffer of size hash_len.
* @param hash_len Length of the output hash (in bytes). Should be approximately bit size of curve group order.
* @param hash_prefix prefix for hash function.
*/
status_t hash_buffer_to_bytes(uint8_t *input_buf, int input_len, uint8_t *output_buf, int hash_len, uint8_t hash_prefix)
{
LEAVE_IF(input_buf == NULL || output_buf == NULL, "uninitialized argument.");
int i, new_input_len = input_len + 2; // extra byte for prefix
uint8_t first_block = 0;
uint8_t new_input[new_input_len+1];
// printf("orig input => \n");
// print_as_hex(input_buf, input_len);
memset(new_input, 0, new_input_len+1);
new_input[0] = first_block; // block number (always 0 by default)
new_input[1] = hash_prefix; // set hash prefix
memcpy((uint8_t *)(new_input+2), input_buf, input_len); // copy input bytes
// printf("new input => \n");
// print_as_hex(new_input, new_input_len);
// prepare output buf
memset(output_buf, 0, hash_len);
if (hash_len <= SHA_LEN) {
uint8_t md[SHA_LEN+1];
SHA_FUNC(md, new_input, new_input_len);
memcpy(output_buf, md, hash_len);
}
else {
// apply variable-size hash technique to get desired size
// determine block count.
int blocks = (int) ceil(((double) hash_len) / SHA_LEN);
//debug("Num blocks needed: %d\n", blocks);
uint8_t md[SHA_LEN+1];
uint8_t md2[(blocks * SHA_LEN)+1];
uint8_t *target_buf = md2;
for(i = 0; i < blocks; i++) {
/* compute digest = SHA-2( i || prefix || input_buf ) || ... || SHA-2( n-1 || prefix || input_buf ) */
target_buf += (i * SHA_LEN);
new_input[0] = (uint8_t) i;
//debug("input %d => ", i);
//print_as_hex(new_input, new_input_len);
SHA_FUNC(md, new_input, new_input_len);
memcpy(target_buf, md, hash_len);
//debug("block %d => ", i);
//print_as_hex(md, SHA_LEN);
memset(md, 0, SHA_LEN);
}
// copy back to caller
memcpy(output_buf, md2, hash_len);
}
return ELEMENT_OK;
}
status_t element_to_key(element_t e, uint8_t *data, int data_len, uint8_t label)
{
LEAVE_IF(e->isInitialized != TRUE, "uninitialized argument.");
// adds an extra null byte by default - will use this last byte for the label
int d_len = element_length(e), digest_len = SHA_LEN;
uint8_t d[d_len + 1];
memset(d, 0, d_len);
// write e to a tmp buf
if(d_len > 0 && digest_len <= data_len) {
element_to_bytes(d, d_len, e);
d[d_len-1] = label;
#ifdef DEBUG
printf("%s: bytes form....\n", __FUNCTION__);
print_as_hex(d, d_len);
#endif
// hash buf using md_map_sh256 and store data_len bytes in data
uint8_t digest[digest_len + 1];
memset(digest, 0, digest_len);
SHA_FUNC(digest, d, d_len);
memcpy(data, digest, digest_len);
#ifdef DEBUG
printf("%s: digest: ", __FUNCTION__);
print_as_hex(data, digest_len);
#endif
return ELEMENT_OK;
}
return ELEMENT_INVALID_ARG;
}
status_t element_from_hash(element_t e, unsigned char *data, int len)
{
LEAVE_IF(e->isInitialized == FALSE, "uninitialized argument.");
GroupType type = e->type;
status_t result = ELEMENT_OK;
int digest_len = SHA_LEN;
unsigned char digest[digest_len + 1];
memset(digest, 0, digest_len);
SHA_FUNC(digest, data, len);
#ifdef DEBUG
printf("%s: digest: ", __FUNCTION__);
print_as_hex(digest, digest_len);
#endif
switch(type) {
case ZR: bn_read_bin(e->bn, digest, digest_len);
if(bn_cmp(e->bn, e->order) == CMP_GT) bn_mod(e->bn, e->bn, e->order);
// bn_print(e->bn);
break;
case G1: g1_map(e->g1, digest, digest_len);
break;
case G2: g2_map(e->g2, digest, digest_len);
break;
default:
result = ELEMENT_INVALID_TYPES;
break;
}
return result;
}
status_t hash_buffer_to_bytes(uint8_t *input, int input_len, uint8_t *output, int output_len, uint8_t label)
{
LEAVE_IF(input == NULL || output == NULL, "uninitialized argument.");
// adds an extra null byte by default - will use this last byte for the label
int digest_len = SHA_LEN;
if(digest_len <= output_len) {
// hash buf using md_map_sh256 and store data_len bytes in data
uint8_t digest[digest_len + 1];
memset(digest, 0, digest_len);
SHA_FUNC(digest, input, input_len);
memcpy(output, digest, digest_len);
#ifdef DEBUG
printf("%s: digest: ", __FUNCTION__);
print_as_hex(output, digest_len);
#endif
return ELEMENT_OK;
}
return ELEMENT_INVALID_ARG;
}
status_t element_from_hash(element_t e, unsigned char *data, int len)
{
LEAVE_IF(e->isInitialized == FALSE, "uninitialized argument.");
GroupType type = e->type;
status_t result = ELEMENT_OK;
int digest_len = SHA_LEN;
unsigned char digest[digest_len + 1];
memset(digest, 0, digest_len);
SHA_FUNC(digest, data, len);
switch(type) {
case ZR: bn_read_bin(e->bn, digest, digest_len);
break;
case G1: g1_map(e->g1, digest, digest_len);
break;
case G2: g2_map(e->g2, digest, digest_len);
break;
default:
result = ELEMENT_INVALID_TYPES;
break;
}
return result;
}
