114 lines
2.8 KiB
C
114 lines
2.8 KiB
C
/*
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This file is for the Gao-Mateer FFT
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sse http://www.math.clemson.edu/~sgao/papers/GM10.pdf
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*/
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#include "fft.h"
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#include "vec.h"
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/* input: in, polynomial in bitsliced form */
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/* output: in, result of applying the radix conversions on in */
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static void radix_conversions(uint64_t *in) {
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int i, j, k;
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const uint64_t mask[5][2] = {
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{0x8888888888888888, 0x4444444444444444},
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{0xC0C0C0C0C0C0C0C0, 0x3030303030303030},
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{0xF000F000F000F000, 0x0F000F000F000F00},
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{0xFF000000FF000000, 0x00FF000000FF0000},
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{0xFFFF000000000000, 0x0000FFFF00000000}
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};
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const uint64_t s[5][GFBITS] = {
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#include "scalars.inc"
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};
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//
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for (j = 0; j <= 4; j++) {
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for (i = 0; i < GFBITS; i++) {
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for (k = 4; k >= j; k--) {
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in[i] ^= (in[i] & mask[k][0]) >> (1 << k);
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in[i] ^= (in[i] & mask[k][1]) >> (1 << k);
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}
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}
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PQCLEAN_MCELIECE348864F_VEC_vec_mul(in, in, s[j]); // scaling
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}
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}
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/* input: in, result of applying the radix conversions to the input polynomial */
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/* output: out, evaluation results (by applying the FFT butterflies) */
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static void butterflies(uint64_t out[][ GFBITS ], const uint64_t *in) {
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int i, j, k, s, b;
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uint64_t tmp[ GFBITS ];
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uint64_t consts[ 63 ][ GFBITS ] = {
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#include "consts.inc"
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};
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const vec powers[ 64 ][ GFBITS ] = {
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#include "powers.inc"
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};
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uint64_t consts_ptr = 0;
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const unsigned char reversal[64] = {
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0, 32, 16, 48, 8, 40, 24, 56,
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4, 36, 20, 52, 12, 44, 28, 60,
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2, 34, 18, 50, 10, 42, 26, 58,
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6, 38, 22, 54, 14, 46, 30, 62,
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1, 33, 17, 49, 9, 41, 25, 57,
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5, 37, 21, 53, 13, 45, 29, 61,
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3, 35, 19, 51, 11, 43, 27, 59,
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7, 39, 23, 55, 15, 47, 31, 63
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};
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// boradcast
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for (j = 0; j < 64; j++) {
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for (i = 0; i < GFBITS; i++) {
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out[j][i] = (in[i] >> reversal[j]) & 1;
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out[j][i] = -out[j][i];
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}
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}
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// butterflies
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for (i = 0; i <= 5; i++) {
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s = 1 << i;
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for (j = 0; j < 64; j += 2 * s) {
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for (k = j; k < j + s; k++) {
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PQCLEAN_MCELIECE348864F_VEC_vec_mul(tmp, out[k + s], consts[ consts_ptr + (k - j) ]);
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for (b = 0; b < GFBITS; b++) {
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out[k][b] ^= tmp[b];
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}
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for (b = 0; b < GFBITS; b++) {
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out[k + s][b] ^= out[k][b];
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}
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}
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}
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consts_ptr += ((uint64_t)1 << i);
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}
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//
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// adding the part contributed by x^64
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for (i = 0; i < 64; i++) {
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for (b = 0; b < GFBITS; b++) {
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out[i][b] ^= powers[i][b];
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}
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}
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}
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void PQCLEAN_MCELIECE348864F_VEC_fft(vec out[][ GFBITS ], vec *in) {
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radix_conversions(in);
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butterflies(out, in);
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}
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