mirror of
https://github.com/henrydcase/pqc.git
synced 2024-11-23 07:59:01 +00:00
94 lines
2.9 KiB
C
94 lines
2.9 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
|
|
*/
|
|
|
|
#define MASK_N2 ((((uint64_t) 1) << PARAM_N2) - 1)
|
|
|
|
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_HQC192_CLEAN_repetition_code_encode(uint64_t *em, const uint64_t *m) {
|
|
uint16_t i, j, bit, idx_r;
|
|
uint32_t pos_r;
|
|
uint64_t *p64 = em;
|
|
const uint64_t mask[2][2] = {{0x0UL, 0x0UL}, {0x7FFFFFFFFFFFFFFUL, 0x3FFFFFFFFFFFFFFUL}};
|
|
for (i = 0; i < VEC_N1_SIZE_64 - 1; i++) {
|
|
for (j = 0; j < 64; j++) {
|
|
bit = (m[i] >> j) & 0x1;
|
|
pos_r = PARAM_N2 * ((i << 6) + j);
|
|
idx_r = (pos_r & 0x3f);
|
|
p64[pos_r >> 6] ^= mask[bit][0] << idx_r;
|
|
p64[(pos_r >> 6) + 1] ^= mask[bit][1] >> ((63 - idx_r));
|
|
}
|
|
}
|
|
|
|
for (j = 0; j < (PARAM_N1 & 0x3f); j++) {
|
|
bit = (m[VEC_N1_SIZE_64 - 1] >> j) & 0x1;
|
|
pos_r = PARAM_N2 * (((VEC_N1_SIZE_64 - 1) << 6) + j);
|
|
idx_r = (pos_r & 0x3f);
|
|
p64[pos_r >> 6] ^= mask[bit][0] << idx_r;
|
|
p64[(pos_r >> 6) + 1] ^= mask[bit][1] >> ((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_HQC192_CLEAN_repetition_code_decode(uint64_t *m, const uint64_t *em) {
|
|
size_t t = 0;
|
|
uint32_t b, bn, bi, c, cn, ci;
|
|
uint64_t cx, ones;
|
|
uint64_t mask;
|
|
|
|
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);
|
|
mask = (uint64_t) (-((int64_t) (cn ^ (bn + 1))) >> 63); // cn != bn+1
|
|
ones = popcount(((em[bn] >> bi) & MASK_N2) | (cx & ~mask));
|
|
m[t >> 6] |= (uint64_t) ((((PARAM_T - ones) >> 31) & 1) << (t & 63));
|
|
t++;
|
|
}
|
|
}
|