-rw-r--r-- 1857 libmceliece-20240812/crypto_kem/460896/vec/vec.c raw
// 20221230 djb: add linker line

// linker define vec_mul vec_sq vec_inv

#include "vec.h"

#include "params.h"

void vec_mul(vec * h, const vec * f, const vec * g)
{
	int i, j;
	vec buf[ 2*GFBITS-1 ];

	for (i = 0; i < 2*GFBITS-1; i++)
		buf[i] = 0;

	for (i = 0; i < GFBITS; i++)
	for (j = 0; j < GFBITS; j++)
		buf[i+j] ^= f[i] & g[j];
		
	for (i = 2*GFBITS-2; i >= GFBITS; i--)
	{
		buf[i-GFBITS+4] ^= buf[i]; 
		buf[i-GFBITS+3] ^= buf[i]; 
		buf[i-GFBITS+1] ^= buf[i]; 
		buf[i-GFBITS+0] ^= buf[i]; 
	}

	for (i = 0; i < GFBITS; i++)
		h[i] = buf[i];
}

/* bitsliced field squarings */
void vec_sq(vec * out, vec * in)
{
	int i;
	vec result[GFBITS], t;

	t = in[11] ^ in[12];

	result[0] = in[0] ^ in[11];
	result[1] = in[7] ^ t;
	result[2] = in[1] ^ in[7];
	result[3] = in[8] ^ t;
	result[4] = in[2] ^ in[7];
	result[4] = result[4] ^ in[8];
	result[4] = result[4] ^ t;
	result[5] = in[7] ^ in[9];
	result[6] = in[3] ^ in[8];
	result[6] = result[6] ^ in[9];
	result[6] = result[6] ^ in[12];
	result[7] = in[8] ^ in[10];
	result[8] = in[4] ^ in[9];
	result[8] = result[8] ^ in[10];
	result[9] = in[9] ^ in[11];
	result[10] = in[5] ^ in[10];
	result[10] = result[10] ^ in[11];
	result[11] = in[10] ^ in[12];
	result[12] = in[6] ^ t;

	for (i = 0; i < GFBITS; i++)
		out[i] = result[i];
}

/* bitsliced field inverses */
void vec_inv(vec * out, vec * in)
{
	vec tmp_11[ GFBITS ];
	vec tmp_1111[ GFBITS ];

	vec_copy(out, in);

	vec_sq(out, out);
	vec_mul(tmp_11, out, in); // ^11

	vec_sq(out, tmp_11);
	vec_sq(out, out);
	vec_mul(tmp_1111, out, tmp_11); // ^1111

	vec_sq(out, tmp_1111);
	vec_sq(out, out);
	vec_sq(out, out);
	vec_sq(out, out);
	vec_mul(out, out, tmp_1111); // ^11111111

	vec_sq(out, out);
	vec_sq(out, out);
	vec_sq(out, out);
	vec_sq(out, out);
	vec_mul(out, out, tmp_1111); // ^111111111111

	vec_sq(out, out); // ^1111111111110
}