#include "cbd.h" #include "params.h" #include <stdint.h> /************************************************* * Name: load32_littleendian * * Description: load 4 bytes into a 32-bit integer * in little-endian order * * Arguments: - const uint8_t *x: pointer to input byte array * * Returns 32-bit unsigned integer loaded from x **************************************************/ static uint32_t load32_littleendian(const uint8_t x[4]) { uint32_t r; r = (uint32_t)x[0]; r |= (uint32_t)x[1] << 8; r |= (uint32_t)x[2] << 16; r |= (uint32_t)x[3] << 24; return r; } /************************************************* * Name: load24_littleendian * * Description: load 3 bytes into a 32-bit integer * in little-endian order. * This function is only needed for Kyber-512 * * Arguments: - const uint8_t *x: pointer to input byte array * * Returns 32-bit unsigned integer loaded from x (most significant byte is zero) **************************************************/ /************************************************* * Name: cbd2 * * Description: Given an array of uniformly random bytes, compute * polynomial with coefficients distributed according to * a centered binomial distribution with parameter eta=2 * * Arguments: - poly *r: pointer to output polynomial * - const uint8_t *buf: pointer to input byte array **************************************************/ static void cbd2(poly *r, const uint8_t buf[2 * KYBER_N / 4]) { unsigned int i, j; uint32_t t, d; int16_t a, b; for (i = 0; i < KYBER_N / 8; i++) { t = load32_littleendian(buf + 4 * i); d = t & 0x55555555; d += (t >> 1) & 0x55555555; for (j = 0; j < 8; j++) { a = (d >> (4 * j + 0)) & 0x3; b = (d >> (4 * j + 2)) & 0x3; r->coeffs[8 * i + j] = a - b; } } } /************************************************* * Name: cbd3 * * Description: Given an array of uniformly random bytes, compute * polynomial with coefficients distributed according to * a centered binomial distribution with parameter eta=3. * This function is only needed for Kyber-512 * * Arguments: - poly *r: pointer to output polynomial * - const uint8_t *buf: pointer to input byte array **************************************************/ void PQCLEAN_KYBER768_CLEAN_poly_cbd_eta1(poly *r, const uint8_t buf[KYBER_ETA1 * KYBER_N / 4]) { cbd2(r, buf); } void PQCLEAN_KYBER768_CLEAN_poly_cbd_eta2(poly *r, const uint8_t buf[KYBER_ETA2 * KYBER_N / 4]) { cbd2(r, buf); }