mirror of
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52 lines
1.6 KiB
C
52 lines
1.6 KiB
C
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/*---------------------------------------------------------------------
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This file has been adapted from the implementation
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(available at, Public Domain https://github.com/pq-crystals/kyber)
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of "CRYSTALS – Kyber: a CCA-secure module-lattice-based KEM"
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by : Joppe Bos, Leo Ducas, Eike Kiltz, Tancrede Lepoint,
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Vadim Lyubashevsky, John M. Schanck, Peter Schwabe & Damien stehle
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----------------------------------------------------------------------*/
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#include "SABER_params.h"
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#include "api.h"
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#include "cbd.h"
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#include <stdint.h>
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static uint64_t load_littleendian(const unsigned char *x, int bytes) {
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int i;
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uint64_t r = x[0];
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for (i = 1; i < bytes; i++) {
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r |= (uint64_t)x[i] << (8 * i);
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}
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return r;
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}
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void PQCLEAN_LIGHTSABER_CLEAN_cbd(uint16_t *r, const unsigned char *buf) {
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uint16_t Qmod_minus1 = SABER_Q - 1;
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uint64_t t, d, a[4], b[4];
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int i, j;
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for (i = 0; i < SABER_N / 4; i++) {
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t = load_littleendian(buf + 5 * i, 5);
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d = 0;
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for (j = 0; j < 5; j++) {
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d += (t >> j) & 0x0842108421UL;
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}
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a[0] = d & 0x1f;
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b[0] = (d >> 5) & 0x1f;
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a[1] = (d >> 10) & 0x1f;
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b[1] = (d >> 15) & 0x1f;
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a[2] = (d >> 20) & 0x1f;
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b[2] = (d >> 25) & 0x1f;
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a[3] = (d >> 30) & 0x1f;
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b[3] = (d >> 35);
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r[4 * i + 0] = (uint16_t)(a[0] - b[0]) & Qmod_minus1;
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r[4 * i + 1] = (uint16_t)(a[1] - b[1]) & Qmod_minus1;
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r[4 * i + 2] = (uint16_t)(a[2] - b[2]) & Qmod_minus1;
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r[4 * i + 3] = (uint16_t)(a[3] - b[3]) & Qmod_minus1;
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}
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}
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