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pqcrypto/crypto_kem/ntruhps4096821/avx2/poly_r2_inv.c
2021-03-24 21:02:46 +00:00

90 lines
2.9 KiB
C

#include "poly.h"
#include "poly_r2_inv.h"
// TODO this costs 1764 cycles.. (implementing as S3_to_bytes results in 2108)
// This can be implemented nicely in assembly using pdep / pext functions
void PQCLEAN_NTRUHPS4096821_AVX2_poly_R2_tobytes(unsigned char *out, const poly *a) {
int i, j, k;
for (i = 0; i < 16; i++) {
for (k = 0; k < 8; k++) {
out[i * 8 + k] = 0;
for (j = 0; j < 8; j++) {
if ((i * 8 + k) * 8 + j < NTRU_N) {
out[i * 8 + k] |= (a->coeffs[(i * 8 + k) * 8 + j] & 1) << j;
}
}
}
}
}
void PQCLEAN_NTRUHPS4096821_AVX2_poly_R2_frombytes(poly *a, const unsigned char *in) {
int i, j, k;
for (i = 0; i < 16; i++) {
for (k = 0; k < 8; k++) {
for (j = 0; j < 8; j++) {
if ((i * 8 + k) * 8 + j < NTRU_N) {
a->coeffs[(i * 8 + k) * 8 + j] = (in[i * 8 + k] >> j) & 1;
}
}
}
}
}
static void _poly_R2_mul(unsigned char r[128], unsigned char a[128], unsigned char b[128]) {
// TODO: Try to avoid copying input
int i;
union {
unsigned char b[128];
__m256i b_x32[4];
} rt;
PQCLEAN_NTRUHPS4096821_AVX2_poly_R2_mul(rt.b, a, b);
for (i = 0; i < 128; i++) {
r[i] = rt.b[i];
}
}
void PQCLEAN_NTRUHPS4096821_AVX2_poly_R2_inv(poly *r, const poly *a) {
union {
unsigned char s[128];
__m256i s_x32[4];
} squares[13];
#define s(x) squares[(x)].s
// This relies on the following addition chain:
// 1, 2, 3, 6, 12, 24, 48, 51, 102, 204, 408, 816, 819
PQCLEAN_NTRUHPS4096821_AVX2_poly_R2_tobytes(s(0), a); // TODO alignment
PQCLEAN_NTRUHPS4096821_AVX2_square_1_821(s(1), s(0));
_poly_R2_mul(s(1), s(1), s(0));
PQCLEAN_NTRUHPS4096821_AVX2_square_1_821(s(2), s(1));
_poly_R2_mul(s(2), s(2), s(0));
PQCLEAN_NTRUHPS4096821_AVX2_square_3_821(s(3), s(2));
_poly_R2_mul(s(3), s(3), s(2));
PQCLEAN_NTRUHPS4096821_AVX2_square_6_821(s(4), s(3));
_poly_R2_mul(s(4), s(4), s(3));
PQCLEAN_NTRUHPS4096821_AVX2_square_12_821(s(5), s(4));
_poly_R2_mul(s(5), s(5), s(4));
PQCLEAN_NTRUHPS4096821_AVX2_square_24_821(s(6), s(5));
_poly_R2_mul(s(6), s(6), s(5));
PQCLEAN_NTRUHPS4096821_AVX2_square_3_821(s(7), s(6));
_poly_R2_mul(s(7), s(7), s(2));
PQCLEAN_NTRUHPS4096821_AVX2_square_51_821(s(8), s(7));
_poly_R2_mul(s(8), s(8), s(7));
PQCLEAN_NTRUHPS4096821_AVX2_square_102_821(s(9), s(8));
_poly_R2_mul(s(9), s(9), s(8));
PQCLEAN_NTRUHPS4096821_AVX2_square_204_821(s(10), s(9));
_poly_R2_mul(s(10), s(10), s(9));
PQCLEAN_NTRUHPS4096821_AVX2_square_408_821(s(11), s(10));
_poly_R2_mul(s(11), s(11), s(10));
PQCLEAN_NTRUHPS4096821_AVX2_square_3_821(s(12), s(11));
_poly_R2_mul(s(12), s(12), s(2));
PQCLEAN_NTRUHPS4096821_AVX2_square_1_821(s(0), s(12));
PQCLEAN_NTRUHPS4096821_AVX2_poly_R2_frombytes(r, s(0));
#undef s
}