101 lines
3.2 KiB
C
101 lines
3.2 KiB
C
#include "parameters.h"
|
|
#include "repetition.h"
|
|
#include <stddef.h>
|
|
#include <stdint.h>
|
|
#include <stdio.h>
|
|
/**
|
|
* @file repetition.c
|
|
* @brief Implementation of repetition codes
|
|
*/
|
|
|
|
static inline int32_t popcount(uint64_t n);
|
|
|
|
/**
|
|
* @brief Encoding each bit in the message m using the repetition code
|
|
*
|
|
*
|
|
* @param[out] em Pointer to an array that is the code word
|
|
* @param[in] m Pointer to an array that is the message
|
|
*/
|
|
void PQCLEAN_HQC256_CLEAN_repetition_code_encode(uint64_t *em, const uint64_t *m) {
|
|
static const uint64_t mask[2][3] = {{0x0UL, 0x0UL, 0x0UL}, {0xFFFFFFFFFFFFFFFFUL, 0xFFFFFFFFFFFFFFFFUL, 0x3FFFFFUL}};
|
|
for (size_t i = 0 ; i < VEC_N1_SIZE_64 - 1 ; i++) {
|
|
for (size_t j = 0 ; j < 64 ; j++) {
|
|
uint8_t bit = (m[i] >> j) & 0x1;
|
|
uint32_t pos_r = PARAM_N2 * ((i << 6) + j);
|
|
uint16_t idx_r = (pos_r & 0x3f);
|
|
uint64_t *p64 = em;
|
|
p64 += pos_r >> 6;
|
|
*p64 ^= mask[bit][0] << idx_r;
|
|
int64_t aux = (41 - idx_r);
|
|
uint64_t aux2 = (aux > 0);
|
|
uint64_t idx2 = aux * aux2;
|
|
*(p64 + 1) ^= mask[bit][1] >> idx2;
|
|
*(p64 + 2) ^= mask[bit][2] >> ((63 - idx_r));
|
|
}
|
|
}
|
|
|
|
for (size_t j = 0 ; j < (PARAM_N1 & 0x3f) ; j++) {
|
|
uint8_t bit = (m[VEC_N1_SIZE_64 - 1] >> j) & 0x1;
|
|
uint32_t pos_r = PARAM_N2 * (((VEC_N1_SIZE_64 - 1) << 6) + j);
|
|
uint16_t idx_r = (pos_r & 0x3f);
|
|
uint64_t *p64 = em;
|
|
p64 += pos_r >> 6;
|
|
*p64 ^= mask[bit][0] << idx_r;
|
|
int64_t aux = (41 - idx_r);
|
|
uint64_t aux2 = (aux > 0);
|
|
uint64_t idx2 = aux * aux2;
|
|
*(p64 + 1) ^= mask[bit][1] >> idx2;
|
|
*(p64 + 2) ^= mask[bit][2] >> ((63 - idx_r));
|
|
}
|
|
}
|
|
|
|
|
|
|
|
/**
|
|
* @brief Compute the Hamming weight of the 64-bit integer n
|
|
*
|
|
* The Hamming weight is computed using a trick described in
|
|
* Henry S. Warren : "Hacker's Delight", chap 5., p. 66
|
|
* @param[out] the Hamming weight of n
|
|
* @param[in] a 64-bit integer n
|
|
*/
|
|
static inline int32_t popcount(uint64_t n) {
|
|
n -= (n >> 1) & 0x5555555555555555UL;
|
|
n = (n & 0x3333333333333333UL) + ((n >> 2) & 0x3333333333333333UL);
|
|
n = (n + (n >> 4)) & 0x0f0f0f0f0f0f0f0fUL;
|
|
return (n * 0x0101010101010101UL) >> 56;
|
|
}
|
|
|
|
|
|
|
|
/**
|
|
* @brief Decoding the code words to a message using the repetition code
|
|
*
|
|
* We use a majority decoding. In fact we have that PARAM_N2 = 2 * PARAM_T + 1, thus,
|
|
* if the Hamming weight of the vector is greater than PARAM_T, the code word is decoded
|
|
* to 1 and 0 otherwise.
|
|
*
|
|
* @param[out] m Pointer to an array that is the message
|
|
* @param[in] em Pointer to an array that is the code word
|
|
*/
|
|
void PQCLEAN_HQC256_CLEAN_repetition_code_decode(uint64_t *m, const uint64_t *em) {
|
|
size_t t = 0, b, bn, bi, c, cn, ci;
|
|
uint64_t cx, ones;
|
|
uint64_t cy;
|
|
|
|
for (b = 0; b < PARAM_N1N2 - PARAM_N2 + 1; b += PARAM_N2) {
|
|
bn = b >> 6;
|
|
bi = b & 63;
|
|
c = b + PARAM_N2 - 1;
|
|
cn = c >> 6;
|
|
ci = c & 63;
|
|
cx = em[cn] << (63 - ci);
|
|
int64_t verif = (cn == (bn + 1));
|
|
cy = em[bn + 1];
|
|
ones = popcount((em[bn] >> bi) | (cx * (1 - verif))) + popcount((1 - verif) * cy + verif * cx);
|
|
m[t >> 6] |= ((uint64_t) (ones > PARAM_T)) << (t & 63);
|
|
t++;
|
|
}
|
|
}
|