136 lines
2.9 KiB
C
136 lines
2.9 KiB
C
/*
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This file is for Niederreiter encryption
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*/
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#include "encrypt.h"
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#include "gf.h"
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#include "params.h"
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#include "randombytes.h"
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#include "util.h"
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#include <stdint.h>
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#include <string.h>
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/* output: e, an error vector of weight t */
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static void gen_e(unsigned char *e) {
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size_t i, j;
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int eq, count;
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uint16_t ind_[ SYS_T * 2 ];
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uint8_t *ind_8 = (uint8_t *)ind_;
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uint16_t ind[ SYS_T * 2 ];
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uint64_t e_int[ (SYS_N + 63) / 64 ];
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uint64_t one = 1;
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uint64_t mask;
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uint64_t val[ SYS_T ];
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while (1) {
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randombytes(ind_8, sizeof(ind_));
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for (i = 0; i < sizeof(ind_); i += 2) {
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ind_[i / 2] = (uint16_t)ind_8[i + 1] << 8 | ind_8[i];
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}
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for (i = 0; i < SYS_T * 2; i++) {
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ind_[i] &= GFMASK;
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}
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count = 0;
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for (i = 0; i < SYS_T * 2; i++) {
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if (ind_[i] < SYS_N) {
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ind[ count++ ] = ind_[i];
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}
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}
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if (count < SYS_T) {
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continue;
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}
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// check for repetition
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eq = 0;
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for (i = 1; i < SYS_T; i++) {
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for (j = 0; j < i; j++) {
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if (ind[i] == ind[j]) {
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eq = 1;
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}
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}
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}
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if (eq == 0) {
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break;
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}
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}
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for (j = 0; j < SYS_T; j++) {
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val[j] = one << (ind[j] & 63);
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}
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for (i = 0; i < (SYS_N + 63) / 64; i++) {
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e_int[i] = 0;
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for (j = 0; j < SYS_T; j++) {
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mask = i ^ (ind[j] >> 6);
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mask -= 1;
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mask >>= 63;
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mask = -mask;
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e_int[i] |= val[j] & mask;
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}
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}
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for (i = 0; i < (SYS_N + 63) / 64 - 1; i++) {
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PQCLEAN_MCELIECE348864F_VEC_store8(e, e_int[i]);
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e += 8;
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}
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for (j = 0; j < (SYS_N % 64); j += 8) {
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e[ j / 8 ] = (e_int[i] >> j) & 0xFF;
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}
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}
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/* input: public key pk, error vector e */
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/* output: syndrome s */
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static void syndrome(unsigned char *s, const unsigned char *pk, const unsigned char *e) {
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uint64_t b;
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const uint8_t *e_ptr8 = e + SYND_BYTES;
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const uint8_t *pk_ptr8;
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int i, j;
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//
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for (i = 0; i < SYND_BYTES; i++) {
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s[i] = e[i];
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}
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for (i = 0; i < PK_NROWS; i++) {
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pk_ptr8 = pk + PK_ROW_BYTES * i;
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b = 0;
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for (j = 0; j < PK_NCOLS / 64; j++) {
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b ^= PQCLEAN_MCELIECE348864F_VEC_load8(pk_ptr8 + 8 * j) & PQCLEAN_MCELIECE348864F_VEC_load8(e_ptr8 + 8 * j);
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}
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b ^= PQCLEAN_MCELIECE348864F_VEC_load4(pk_ptr8 + 8 * j) & PQCLEAN_MCELIECE348864F_VEC_load4(e_ptr8 + 8 * j);
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b ^= b >> 32;
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b ^= b >> 16;
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b ^= b >> 8;
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b ^= b >> 4;
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b ^= b >> 2;
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b ^= b >> 1;
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b &= 1;
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s[ i / 8 ] ^= (b << (i % 8));
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}
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}
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void PQCLEAN_MCELIECE348864F_VEC_encrypt(unsigned char *s, unsigned char *e, const unsigned char *pk) {
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gen_e(e);
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syndrome(s, pk, e);
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}
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