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pqcrypto/crypto_kem/mceliece6688128/vec/encrypt.c

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/*
This file is for Niederreiter encryption
*/
#include "encrypt.h"
#include "params.h"
#include "randombytes.h"
#include "util.h"
#include <assert.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include "gf.h"
/* output: e, an error vector of weight t */
static void gen_e(unsigned char *e) {
size_t i, j;
int eq, count;
uint16_t ind[ SYS_T * 2 ];
uint8_t *ind8 = (uint8_t *)ind;
uint32_t ind32[ SYS_T * 2 ];
uint64_t e_int[ (SYS_N + 63) / 64 ];
uint64_t one = 1;
uint64_t mask;
uint64_t val[ SYS_T ];
while (1) {
randombytes(ind8, sizeof(ind));
for (i = 0; i < sizeof(ind); i += 2) {
ind[i / 2] = (uint16_t)ind8[i + 1] << 8 | ind8[i];
}
for (i = 0; i < SYS_T * 2; i++) {
ind[i] &= GFMASK;
}
// moving and counting indices in the correct range
count = 0;
for (i = 0; i < SYS_T * 2; i++) {
if (ind[i] < SYS_N) {
ind32[ count++ ] = ind[i];
}
}
if (count < SYS_T) {
continue;
}
// check for repetition
eq = 0;
for (i = 1; i < SYS_T; i++) {
for (j = 0; j < i; j++) {
if (ind32[i] == ind32[j]) {
eq = 1;
}
}
}
if (eq == 0) {
break;
}
}
for (j = 0; j < SYS_T; j++) {
val[j] = one << (ind32[j] & 63);
}
for (i = 0; i < (SYS_N + 63) / 64; i++) {
e_int[i] = 0;
for (j = 0; j < SYS_T; j++) {
mask = i ^ (ind32[j] >> 6);
mask -= 1;
mask >>= 63;
mask = -mask;
e_int[i] |= val[j] & mask;
}
}
for (i = 0; i < (SYS_N + 63) / 64 - 1; i++) {
PQCLEAN_MCELIECE6688128_VEC_store8(e, e_int[i]);
e += 8;
}
for (j = 0; j < (SYS_N % 64); j += 8) {
e[ j / 8 ] = (e_int[i] >> j) & 0xFF;
}
}
/* input: public key pk, error vector e */
/* output: syndrome s */
static void syndrome(unsigned char *s, const unsigned char *pk, const unsigned char *e) {
uint64_t b;
const uint8_t *e_ptr8 = e + SYND_BYTES;
const uint8_t *pk_ptr8;
int i, j;
//
for (i = 0; i < SYND_BYTES; i++) {
s[i] = e[i];
}
for (i = 0; i < PK_NROWS; i++) {
pk_ptr8 = pk + PK_ROW_BYTES * i;
b = 0;
for (j = 0; j < PK_NCOLS / 64; j++) {
b ^= PQCLEAN_MCELIECE6688128_VEC_load8(pk_ptr8 + 8 * j) & PQCLEAN_MCELIECE6688128_VEC_load8(e_ptr8 + 8 * j);
}
b ^= PQCLEAN_MCELIECE6688128_VEC_load4(pk_ptr8 + 8 * j) & PQCLEAN_MCELIECE6688128_VEC_load4(e_ptr8 + 8 * j);
b ^= b >> 32;
b ^= b >> 16;
b ^= b >> 8;
b ^= b >> 4;
b ^= b >> 2;
b ^= b >> 1;
b &= 1;
s[ i / 8 ] ^= (b << (i % 8));
}
}
/* input: public key pk */
/* output: error vector e, syndrome s */
void PQCLEAN_MCELIECE6688128_VEC_encrypt(unsigned char *s, unsigned char *e, const unsigned char *pk) {
gen_e(e);
syndrome(s, pk, e);
}