177 lines
5.1 KiB
C
177 lines
5.1 KiB
C
#include "gf.h"
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#include "parameters.h"
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#include <stdint.h>
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/**
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* @file gf.c
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* Galois field implementation with multiplication using the pclmulqdq instruction
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*/
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static uint16_t gf_reduce(uint64_t x, size_t deg_x);
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/**
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* Reduces polynomial x modulo primitive polynomial GF_POLY.
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* @returns x mod GF_POLY
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* @param[in] x Polynomial of degree less than 64
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* @param[in] deg_x The degree of polynomial x
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*/
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static uint16_t gf_reduce(uint64_t x, size_t deg_x) {
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uint16_t z1, z2, rmdr, dist;
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uint64_t mod;
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size_t steps, i, j;
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// Deduce the number of steps of reduction
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steps = CEIL_DIVIDE(deg_x - (PARAM_M - 1), PARAM_GF_POLY_M2);
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// Reduce
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for (i = 0; i < steps; ++i) {
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mod = x >> PARAM_M;
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x &= (1 << PARAM_M) - 1;
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x ^= mod;
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z1 = 0;
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rmdr = PARAM_GF_POLY ^ 1;
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for (j = PARAM_GF_POLY_WT - 2; j; --j) {
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z2 = __tzcnt_u16(rmdr);
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dist = (uint16_t) (z2 - z1);
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mod <<= dist;
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x ^= mod;
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rmdr ^= 1 << z2;
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z1 = z2;
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}
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}
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return x;
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}
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/**
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* Multiplies two elements of GF(2^GF_M).
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* @returns the product a*b
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* @param[in] a Element of GF(2^GF_M)
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* @param[in] b Element of GF(2^GF_M)
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*/
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uint16_t PQCLEAN_HQCRMRS256_AVX2_gf_mul(uint16_t a, uint16_t b) {
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__m128i va = _mm_cvtsi32_si128(a);
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__m128i vb = _mm_cvtsi32_si128(b);
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__m128i vab = _mm_clmulepi64_si128(va, vb, 0);
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uint32_t ab = _mm_cvtsi128_si32(vab);
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return gf_reduce(ab, 2 * (PARAM_M - 1));
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}
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/**
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* Compute 16 products in GF(2^GF_M).
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* @returns the product (a0b0,a1b1,...,a15b15) , ai,bi in GF(2^GF_M)
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* @param[in] a 256-bit register where a0,..,a15 are stored as 16 bit integers
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* @param[in] b 256-bit register where b0,..,b15 are stored as 16 bit integer
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*
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*/
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__m256i PQCLEAN_HQCRMRS256_AVX2_gf_mul_vect(__m256i a, __m256i b) {
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__m128i al = _mm256_extractf128_si256(a, 0);
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__m128i ah = _mm256_extractf128_si256(a, 1);
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__m128i bl = _mm256_extractf128_si256(b, 0);
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__m128i bh = _mm256_extractf128_si256(b, 1);
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__m128i abl0 = _mm_clmulepi64_si128(al & CONST128_MASKL, bl & CONST128_MASKL, 0x0);
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abl0 &= CONST128_MIDDLEMASKL;
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abl0 ^= (_mm_clmulepi64_si128(al & CONST128_MASKH, bl & CONST128_MASKH, 0x0) & CONST128_MIDDLEMASKH);
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__m128i abh0 = _mm_clmulepi64_si128(al & CONST128_MASKL, bl & CONST128_MASKL, 0x11);
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abh0 &= CONST128_MIDDLEMASKL;
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abh0 ^= (_mm_clmulepi64_si128(al & CONST128_MASKH, bl & CONST128_MASKH, 0x11) & CONST128_MIDDLEMASKH);
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abl0 = _mm_shuffle_epi8(abl0, CONST128_INDEXL);
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abl0 ^= _mm_shuffle_epi8(abh0, CONST128_INDEXH);
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__m128i abl1 = _mm_clmulepi64_si128(ah & CONST128_MASKL, bh & CONST128_MASKL, 0x0);
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abl1 &= CONST128_MIDDLEMASKL;
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abl1 ^= (_mm_clmulepi64_si128(ah & CONST128_MASKH, bh & CONST128_MASKH, 0x0) & CONST128_MIDDLEMASKH);
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__m128i abh1 = _mm_clmulepi64_si128(ah & CONST128_MASKL, bh & CONST128_MASKL, 0x11);
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abh1 &= CONST128_MIDDLEMASKL;
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abh1 ^= (_mm_clmulepi64_si128(ah & CONST128_MASKH, bh & CONST128_MASKH, 0x11) & CONST128_MIDDLEMASKH);
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abl1 = _mm_shuffle_epi8(abl1, CONST128_INDEXL);
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abl1 ^= _mm_shuffle_epi8(abh1, CONST128_INDEXH);
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__m256i ret = _mm256_set_m128i(abl1, abl0);
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__m256i aux = CONST256_MR0;
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for (int32_t i = 0; i < 7; i++) {
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ret ^= red[i] & _mm256_cmpeq_epi16((ret & aux), aux);
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aux = aux << 1;
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}
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ret &= CONST256_LASTMASK;
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return ret;
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}
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/**
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* Squares an element of GF(2^GF_M).
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* @returns a^2
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* @param[in] a Element of GF(2^GF_M)
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*/
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uint16_t PQCLEAN_HQCRMRS256_AVX2_gf_square(uint16_t a) {
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uint32_t b = a;
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uint32_t s = b & 1;
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for (size_t i = 1; i < PARAM_M; ++i) {
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b <<= 1;
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s ^= b & (1 << 2 * i);
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}
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return gf_reduce(s, 2 * (PARAM_M - 1));
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}
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/**
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* Computes the inverse of an element of GF(2^8),
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* using the addition chain 1 2 3 4 7 11 15 30 60 120 127 254
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* @returns the inverse of a
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* @param[in] a Element of GF(2^GF_M)
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*/
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uint16_t PQCLEAN_HQCRMRS256_AVX2_gf_inverse(uint16_t a) {
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uint16_t inv = a;
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uint16_t tmp1, tmp2;
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inv = PQCLEAN_HQCRMRS256_AVX2_gf_square(a); /* a^2 */
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tmp1 = PQCLEAN_HQCRMRS256_AVX2_gf_mul(inv, a); /* a^3 */
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inv = PQCLEAN_HQCRMRS256_AVX2_gf_square(inv); /* a^4 */
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tmp2 = PQCLEAN_HQCRMRS256_AVX2_gf_mul(inv, tmp1); /* a^7 */
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tmp1 = PQCLEAN_HQCRMRS256_AVX2_gf_mul(inv, tmp2); /* a^11 */
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inv = PQCLEAN_HQCRMRS256_AVX2_gf_mul(tmp1, inv); /* a^15 */
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inv = PQCLEAN_HQCRMRS256_AVX2_gf_square(inv); /* a^30 */
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inv = PQCLEAN_HQCRMRS256_AVX2_gf_square(inv); /* a^60 */
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inv = PQCLEAN_HQCRMRS256_AVX2_gf_square(inv); /* a^120 */
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inv = PQCLEAN_HQCRMRS256_AVX2_gf_mul(inv, tmp2); /* a^127 */
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inv = PQCLEAN_HQCRMRS256_AVX2_gf_square(inv); /* a^254 */
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return inv;
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}
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/**
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* Returns i modulo 2^GF_M-1.
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* i must be less than 2*(2^GF_M-1).
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* Therefore, the return value is either i or i-2^GF_M+1.
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* @returns i mod (2^GF_M-1)
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* @param[in] i The integer whose modulo is taken
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*/
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uint16_t PQCLEAN_HQCRMRS256_AVX2_gf_mod(uint16_t i) {
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uint16_t tmp = (uint16_t) (i - PARAM_GF_MUL_ORDER);
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// mask = 0xffff if (i < GF_MUL_ORDER)
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uint16_t mask = -(tmp >> 15);
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return tmp + (mask & PARAM_GF_MUL_ORDER);
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}
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