55 lines
1.9 KiB
C
55 lines
1.9 KiB
C
#include "sample.h"
|
|
#include "fips202.h"
|
|
|
|
void PQCLEAN_NTRUHRSS701_CLEAN_sample_fg(poly *f, poly *g, const unsigned char uniformbytes[NTRU_SAMPLE_FG_BYTES]) {
|
|
PQCLEAN_NTRUHRSS701_CLEAN_sample_iid_plus(f, uniformbytes);
|
|
PQCLEAN_NTRUHRSS701_CLEAN_sample_iid_plus(g, uniformbytes + NTRU_SAMPLE_IID_BYTES);
|
|
}
|
|
|
|
void PQCLEAN_NTRUHRSS701_CLEAN_sample_rm(poly *r, poly *m, const unsigned char uniformbytes[NTRU_SAMPLE_RM_BYTES]) {
|
|
PQCLEAN_NTRUHRSS701_CLEAN_sample_iid(r, uniformbytes);
|
|
PQCLEAN_NTRUHRSS701_CLEAN_sample_iid(m, uniformbytes + NTRU_SAMPLE_IID_BYTES);
|
|
}
|
|
|
|
void PQCLEAN_NTRUHRSS701_CLEAN_sample_iid(poly *r, const unsigned char uniformbytes[NTRU_SAMPLE_IID_BYTES]) {
|
|
int i;
|
|
/* {0,1,...,255} -> {0,1,2}; Pr[0] = 86/256, Pr[1] = Pr[-1] = 85/256 */
|
|
for (i = 0; i < NTRU_N - 1; i++) {
|
|
r->coeffs[i] = PQCLEAN_NTRUHRSS701_CLEAN_mod3(uniformbytes[i]);
|
|
}
|
|
|
|
r->coeffs[NTRU_N - 1] = 0;
|
|
}
|
|
|
|
void PQCLEAN_NTRUHRSS701_CLEAN_sample_iid_plus(poly *r, const unsigned char uniformbytes[NTRU_SAMPLE_IID_BYTES]) {
|
|
/* Sample r using sample_iid then conditionally flip */
|
|
/* signs of even index coefficients so that <x*r, r> >= 0. */
|
|
|
|
int i;
|
|
uint16_t s = 0;
|
|
|
|
PQCLEAN_NTRUHRSS701_CLEAN_sample_iid(r, uniformbytes);
|
|
|
|
/* Map {0,1,2} -> {0, 1, 2^16 - 1} */
|
|
for (i = 0; i < NTRU_N - 1; i++) {
|
|
r->coeffs[i] = r->coeffs[i] | (-(r->coeffs[i] >> 1));
|
|
}
|
|
|
|
/* s = <x*r, r>. (r[n-1] = 0) */
|
|
for (i = 0; i < NTRU_N - 1; i++) {
|
|
s += (uint16_t)((uint32_t)r->coeffs[i + 1] * (uint32_t)r->coeffs[i]);
|
|
}
|
|
|
|
/* Extract sign of s (sign(0) = 1) */
|
|
s = 1 | (-(s >> 15));
|
|
|
|
for (i = 0; i < NTRU_N; i += 2) {
|
|
r->coeffs[i] = (uint16_t)((uint32_t)s * (uint32_t)r->coeffs[i]);
|
|
}
|
|
|
|
/* Map {0,1,2^16-1} -> {0, 1, 2} */
|
|
for (i = 0; i < NTRU_N; i++) {
|
|
r->coeffs[i] = 3 & (r->coeffs[i] ^ (r->coeffs[i] >> 15));
|
|
}
|
|
}
|