27 lines
699 B
C
27 lines
699 B
C
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#include "sample.h"
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static uint16_t mod3(uint16_t a) {
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uint16_t r;
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int16_t t, c;
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r = (a >> 8) + (a & 0xff); // r mod 255 == a mod 255
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r = (r >> 4) + (r & 0xf); // r' mod 15 == r mod 15
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r = (r >> 2) + (r & 0x3); // r' mod 3 == r mod 3
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r = (r >> 2) + (r & 0x3); // r' mod 3 == r mod 3
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t = r - 3;
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c = t >> 15;
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return (c & r) ^ (~c & t);
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}
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void PQCLEAN_NTRUHRSS701_CLEAN_sample_iid(poly *r, const unsigned char uniformbytes[NTRU_SAMPLE_IID_BYTES]) {
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int i;
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/* {0,1,...,255} -> {0,1,2}; Pr[0] = 86/256, Pr[1] = Pr[-1] = 85/256 */
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for (i = 0; i < NTRU_N - 1; i++) {
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r->coeffs[i] = mod3(uniformbytes[i]);
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}
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r->coeffs[NTRU_N - 1] = 0;
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}
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