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