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147 lines
5.4 KiB
C
147 lines
5.4 KiB
C
#include "ntt.h"
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#include "params.h"
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#include "reduce.h"
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#include <stdint.h>
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/* Code to generate PQCLEAN_KYBER768_CLEAN_zetas and zetas_inv used in the number-theoretic transform:
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#define KYBER_ROOT_OF_UNITY 17
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static const uint8_t tree[128] = {
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0, 64, 32, 96, 16, 80, 48, 112, 8, 72, 40, 104, 24, 88, 56, 120,
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4, 68, 36, 100, 20, 84, 52, 116, 12, 76, 44, 108, 28, 92, 60, 124,
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2, 66, 34, 98, 18, 82, 50, 114, 10, 74, 42, 106, 26, 90, 58, 122,
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6, 70, 38, 102, 22, 86, 54, 118, 14, 78, 46, 110, 30, 94, 62, 126,
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1, 65, 33, 97, 17, 81, 49, 113, 9, 73, 41, 105, 25, 89, 57, 121,
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5, 69, 37, 101, 21, 85, 53, 117, 13, 77, 45, 109, 29, 93, 61, 125,
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3, 67, 35, 99, 19, 83, 51, 115, 11, 75, 43, 107, 27, 91, 59, 123,
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7, 71, 39, 103, 23, 87, 55, 119, 15, 79, 47, 111, 31, 95, 63, 127
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};
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void init_ntt() {
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unsigned int i;
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int16_t tmp[128];
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tmp[0] = MONT;
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for(i=1;i<128;i++)
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tmp[i] = fqmul(tmp[i-1],MONT*KYBER_ROOT_OF_UNITY % KYBER_Q);
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for(i=0;i<128;i++) {
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PQCLEAN_KYBER768_CLEAN_zetas[i] = tmp[tree[i]];
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if(PQCLEAN_KYBER768_CLEAN_zetas[i] > KYBER_Q/2)
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PQCLEAN_KYBER768_CLEAN_zetas[i] -= KYBER_Q;
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if(PQCLEAN_KYBER768_CLEAN_zetas[i] < -KYBER_Q/2)
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PQCLEAN_KYBER768_CLEAN_zetas[i] += KYBER_Q;
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}
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}
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*/
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const int16_t PQCLEAN_KYBER768_CLEAN_zetas[128] = {
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-1044, -758, -359, -1517, 1493, 1422, 287, 202,
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-171, 622, 1577, 182, 962, -1202, -1474, 1468,
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573, -1325, 264, 383, -829, 1458, -1602, -130,
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-681, 1017, 732, 608, -1542, 411, -205, -1571,
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1223, 652, -552, 1015, -1293, 1491, -282, -1544,
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516, -8, -320, -666, -1618, -1162, 126, 1469,
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-853, -90, -271, 830, 107, -1421, -247, -951,
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-398, 961, -1508, -725, 448, -1065, 677, -1275,
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-1103, 430, 555, 843, -1251, 871, 1550, 105,
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422, 587, 177, -235, -291, -460, 1574, 1653,
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-246, 778, 1159, -147, -777, 1483, -602, 1119,
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-1590, 644, -872, 349, 418, 329, -156, -75,
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817, 1097, 603, 610, 1322, -1285, -1465, 384,
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-1215, -136, 1218, -1335, -874, 220, -1187, -1659,
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-1185, -1530, -1278, 794, -1510, -854, -870, 478,
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-108, -308, 996, 991, 958, -1460, 1522, 1628
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};
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/*************************************************
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* Name: fqmul
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*
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* Description: Multiplication followed by Montgomery reduction
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*
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* Arguments: - int16_t a: first factor
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* - int16_t b: second factor
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*
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* Returns 16-bit integer congruent to a*b*R^{-1} mod q
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**************************************************/
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static int16_t fqmul(int16_t a, int16_t b) {
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return PQCLEAN_KYBER768_CLEAN_montgomery_reduce((int32_t)a * b);
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}
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/*************************************************
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* Name: PQCLEAN_KYBER768_CLEAN_ntt
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*
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* Description: Inplace number-theoretic transform (NTT) in Rq.
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* input is in standard order, output is in bitreversed order
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*
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* Arguments: - int16_t r[256]: pointer to input/output vector of elements of Zq
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**************************************************/
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void PQCLEAN_KYBER768_CLEAN_ntt(int16_t r[256]) {
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unsigned int len, start, j, k;
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int16_t t, zeta;
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k = 1;
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for (len = 128; len >= 2; len >>= 1) {
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for (start = 0; start < 256; start = j + len) {
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zeta = PQCLEAN_KYBER768_CLEAN_zetas[k++];
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for (j = start; j < start + len; j++) {
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t = fqmul(zeta, r[j + len]);
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r[j + len] = r[j] - t;
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r[j] = r[j] + t;
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}
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}
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}
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}
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/*************************************************
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* Name: invntt_tomont
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*
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* Description: Inplace inverse number-theoretic transform in Rq and
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* multiplication by Montgomery factor 2^16.
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* Input is in bitreversed order, output is in standard order
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*
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* Arguments: - int16_t r[256]: pointer to input/output vector of elements of Zq
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**************************************************/
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void PQCLEAN_KYBER768_CLEAN_invntt(int16_t r[256]) {
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unsigned int start, len, j, k;
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int16_t t, zeta;
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const int16_t f = 1441; // mont^2/128
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k = 127;
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for (len = 2; len <= 128; len <<= 1) {
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for (start = 0; start < 256; start = j + len) {
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zeta = PQCLEAN_KYBER768_CLEAN_zetas[k--];
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for (j = start; j < start + len; j++) {
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t = r[j];
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r[j] = PQCLEAN_KYBER768_CLEAN_barrett_reduce(t + r[j + len]);
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r[j + len] = r[j + len] - t;
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r[j + len] = fqmul(zeta, r[j + len]);
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}
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}
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}
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for (j = 0; j < 256; j++) {
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r[j] = fqmul(r[j], f);
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}
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}
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/*************************************************
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* Name: PQCLEAN_KYBER768_CLEAN_basemul
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*
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* Description: Multiplication of polynomials in Zq[X]/(X^2-zeta)
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* used for multiplication of elements in Rq in NTT domain
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*
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* Arguments: - int16_t r[2]: pointer to the output polynomial
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* - const int16_t a[2]: pointer to the first factor
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* - const int16_t b[2]: pointer to the second factor
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* - int16_t zeta: integer defining the reduction polynomial
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**************************************************/
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void PQCLEAN_KYBER768_CLEAN_basemul(int16_t r[2], const int16_t a[2], const int16_t b[2], int16_t zeta) {
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r[0] = fqmul(a[1], b[1]);
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r[0] = fqmul(r[0], zeta);
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r[0] += fqmul(a[0], b[0]);
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r[1] = fqmul(a[0], b[1]);
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r[1] += fqmul(a[1], b[0]);
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}
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