76 lines
2.4 KiB
C
76 lines
2.4 KiB
C
#include "poly.h"
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/* Map {0, 1, 2} -> {0,1,q-1} in place */
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void PQCLEAN_NTRUHPS2048509_CLEAN_poly_Z3_to_Zq(poly *r) {
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int i;
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for (i = 0; i < NTRU_N; i++) {
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r->coeffs[i] = r->coeffs[i] | ((-(r->coeffs[i] >> 1)) & (NTRU_Q - 1));
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}
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}
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/* Map {0, 1, q-1} -> {0,1,2} in place */
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void PQCLEAN_NTRUHPS2048509_CLEAN_poly_trinary_Zq_to_Z3(poly *r) {
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int i;
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for (i = 0; i < NTRU_N; i++) {
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r->coeffs[i] = MODQ(r->coeffs[i]);
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r->coeffs[i] = 3 & (r->coeffs[i] ^ (r->coeffs[i] >> (NTRU_LOGQ - 1)));
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}
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}
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void PQCLEAN_NTRUHPS2048509_CLEAN_poly_Sq_mul(poly *r, const poly *a, const poly *b) {
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PQCLEAN_NTRUHPS2048509_CLEAN_poly_Rq_mul(r, a, b);
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PQCLEAN_NTRUHPS2048509_CLEAN_poly_mod_q_Phi_n(r);
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}
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void PQCLEAN_NTRUHPS2048509_CLEAN_poly_S3_mul(poly *r, const poly *a, const poly *b) {
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int i;
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/* Our S3 multiplications do not overflow mod q, */
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/* so we can re-purpose PQCLEAN_NTRUHPS2048509_CLEAN_poly_Rq_mul, as long as we */
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/* follow with an explicit reduction mod q. */
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PQCLEAN_NTRUHPS2048509_CLEAN_poly_Rq_mul(r, a, b);
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for (i = 0; i < NTRU_N; i++) {
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r->coeffs[i] = MODQ(r->coeffs[i]);
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}
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PQCLEAN_NTRUHPS2048509_CLEAN_poly_mod_3_Phi_n(r);
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}
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static void PQCLEAN_NTRUHPS2048509_CLEAN_poly_R2_inv_to_Rq_inv(poly *r, const poly *ai, const poly *a) {
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int i;
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poly b, c;
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poly s;
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// for 0..4
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// ai = ai * (2 - a*ai) mod q
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for (i = 0; i < NTRU_N; i++) {
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b.coeffs[i] = -(a->coeffs[i]);
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}
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for (i = 0; i < NTRU_N; i++) {
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r->coeffs[i] = ai->coeffs[i];
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}
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PQCLEAN_NTRUHPS2048509_CLEAN_poly_Rq_mul(&c, r, &b);
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c.coeffs[0] += 2; // c = 2 - a*ai
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PQCLEAN_NTRUHPS2048509_CLEAN_poly_Rq_mul(&s, &c, r); // s = ai*c
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PQCLEAN_NTRUHPS2048509_CLEAN_poly_Rq_mul(&c, &s, &b);
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c.coeffs[0] += 2; // c = 2 - a*s
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PQCLEAN_NTRUHPS2048509_CLEAN_poly_Rq_mul(r, &c, &s); // r = s*c
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PQCLEAN_NTRUHPS2048509_CLEAN_poly_Rq_mul(&c, r, &b);
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c.coeffs[0] += 2; // c = 2 - a*r
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PQCLEAN_NTRUHPS2048509_CLEAN_poly_Rq_mul(&s, &c, r); // s = r*c
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PQCLEAN_NTRUHPS2048509_CLEAN_poly_Rq_mul(&c, &s, &b);
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c.coeffs[0] += 2; // c = 2 - a*s
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PQCLEAN_NTRUHPS2048509_CLEAN_poly_Rq_mul(r, &c, &s); // r = s*c
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}
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void PQCLEAN_NTRUHPS2048509_CLEAN_poly_Rq_inv(poly *r, const poly *a) {
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poly ai2;
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PQCLEAN_NTRUHPS2048509_CLEAN_poly_R2_inv(&ai2, a);
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PQCLEAN_NTRUHPS2048509_CLEAN_poly_R2_inv_to_Rq_inv(r, &ai2, a);
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}
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