pqc/crypto_kem/mceliece460896f/vec/benes.c

/*
  This file is for Benes network related functions
*/

#include "benes.h"

#include "params.h"
#include "transpose.h"
#include "util.h"
#include "vec.h"

/* middle layers of the benes network */
static void layer_in(uint64_t data[2][64], uint64_t *bits, int lgs) {
    int i, j, s;

    uint64_t d;

    s = 1 << lgs;

    for (i = 0; i < 64; i += s * 2) {
        for (j = i; j < i + s; j++) {

            d = (data[0][j + 0] ^ data[0][j + s]);
            d &= (*bits++);
            data[0][j + 0] ^= d;
            data[0][j + s] ^= d;

            d = (data[1][j + 0] ^ data[1][j + s]);
            d &= (*bits++);
            data[1][j + 0] ^= d;
            data[1][j + s] ^= d;
        }
    }
}

/* first and last layers of the benes network */
static void layer_ex(uint64_t *data, uint64_t *bits, int lgs) {
    int i, j, s;

    uint64_t d;

    s = 1 << lgs;

    for (i = 0; i < 128; i += s * 2) {
        for (j = i; j < i + s; j++) {

            d = (data[j + 0] ^ data[j + s]);
            d &= (*bits++);
            data[j + 0] ^= d;
            data[j + s] ^= d;
        }
    }
}

/* input: r, sequence of bits to be permuted */
/*        bits, condition bits of the Benes network */
/*        rev, 0 for normal application; !0 for inverse */
/* output: r, permuted bits */
void PQCLEAN_MCELIECE460896F_VEC_benes(vec *r, const unsigned char *bits, int rev) {
    int i, iter, inc;

    const unsigned char *bits_ptr;

    uint64_t r_int_v[2][64];
    uint64_t r_int_h[2][64];
    uint64_t b_int_v[64];
    uint64_t b_int_h[64];

    //

    if (rev) {
        bits_ptr = bits + 12288;
        inc = -1024;
    } else     {
        bits_ptr = bits;
        inc = 0;
    }

    for (i = 0; i < 64; i++) {
        r_int_v[0][i] = r[i * 2 + 0];
        r_int_v[1][i] = r[i * 2 + 1];
    }

    PQCLEAN_MCELIECE460896F_VEC_transpose_64x64(r_int_h[0], r_int_v[0]);
    PQCLEAN_MCELIECE460896F_VEC_transpose_64x64(r_int_h[1], r_int_v[1]);

    for (iter = 0; iter <= 6; iter++) {
        for (i = 0; i < 64; i++) {
            b_int_v[i] = PQCLEAN_MCELIECE460896F_VEC_load8(bits_ptr);
            bits_ptr += 8;
        }

        bits_ptr += inc;

        PQCLEAN_MCELIECE460896F_VEC_transpose_64x64(b_int_h, b_int_v);

        layer_ex(r_int_h[0], b_int_h, iter);
    }

    PQCLEAN_MCELIECE460896F_VEC_transpose_64x64(r_int_v[0], r_int_h[0]);
    PQCLEAN_MCELIECE460896F_VEC_transpose_64x64(r_int_v[1], r_int_h[1]);

    for (iter = 0; iter <= 5; iter++) {
        for (i = 0; i < 64; i++) {
            b_int_v[i] = PQCLEAN_MCELIECE460896F_VEC_load8(bits_ptr);
            bits_ptr += 8;
        }
        bits_ptr += inc;

        layer_in(r_int_v, b_int_v, iter);
    }

    for (iter = 4; iter >= 0; iter--) {
        for (i = 0; i < 64; i++) {
            b_int_v[i] = PQCLEAN_MCELIECE460896F_VEC_load8(bits_ptr);
            bits_ptr += 8;
        }
        bits_ptr += inc;

        layer_in(r_int_v, b_int_v, iter);
    }

    PQCLEAN_MCELIECE460896F_VEC_transpose_64x64(r_int_h[0], r_int_v[0]);
    PQCLEAN_MCELIECE460896F_VEC_transpose_64x64(r_int_h[1], r_int_v[1]);

    for (iter = 6; iter >= 0; iter--) {
        for (i = 0; i < 64; i++) {
            b_int_v[i] = PQCLEAN_MCELIECE460896F_VEC_load8(bits_ptr);
            bits_ptr += 8;
        }

        bits_ptr += inc;

        PQCLEAN_MCELIECE460896F_VEC_transpose_64x64(b_int_h, b_int_v);

        layer_ex(r_int_h[0], b_int_h, iter);
    }

    PQCLEAN_MCELIECE460896F_VEC_transpose_64x64(r_int_v[0], r_int_h[0]);
    PQCLEAN_MCELIECE460896F_VEC_transpose_64x64(r_int_v[1], r_int_h[1]);

    for (i = 0; i < 64; i++) {
        r[i * 2 + 0] = r_int_v[0][i];
        r[i * 2 + 1] = r_int_v[1][i];
    }
}