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cc551546bf
pqcrypto/crypto_kem/ledakemlt12/clean/gf2x_arith.c
Leon cc551546bf cleaning & fixing gcc warnings
2019-05-24 18:38:54 +02:00

380 lines
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#include "gf2x_arith.h"
#include <string.h> // memset(...)
#include <assert.h>
/* allows the second operand to be shorter than the first */
/* the result should be as large as the first operand*/
static inline void gf2x_add_asymm(const size_t nr, DIGIT Res[],
const size_t na, const DIGIT A[],
const size_t nb, const DIGIT B[]) {
assert(nr >= na && na >= nb);
size_t i;
size_t delta = na - nb;
for (i = 0; i < delta; i++) {
Res[i] = A[i];
}
for (i = 0; i < nb; i++) {
Res[i + delta] = A[i + delta] ^ B[i];
}
}
/* PRE: MAX ALLOWED ROTATION AMOUNT : DIGIT_SIZE_b */
void PQCLEAN_LEDAKEMLT12_CLEAN_right_bit_shift_n(const int length, DIGIT in[], const int amount) {
assert(amount < DIGIT_SIZE_b);
if ( amount == 0 ) {
return;
}
int j;
DIGIT mask;
mask = ((DIGIT)0x01 << amount) - 1;
for (j = length - 1; j > 0 ; j--) {
in[j] >>= amount;
in[j] |= (in[j - 1] & mask) << (DIGIT_SIZE_b - amount);
}
in[j] >>= amount;
}
/* PRE: MAX ALLOWED ROTATION AMOUNT : DIGIT_SIZE_b */
void PQCLEAN_LEDAKEMLT12_CLEAN_left_bit_shift_n(const int length, DIGIT in[], const int amount) {
assert(amount < DIGIT_SIZE_b);
if ( amount == 0 ) {
return;
}
int j;
DIGIT mask;
mask = ~(((DIGIT)0x01 << (DIGIT_SIZE_b - amount)) - 1);
for (j = 0 ; j < length - 1 ; j++) {
in[j] <<= amount;
in[j] |= (in[j + 1] & mask) >> (DIGIT_SIZE_b - amount);
}
in[j] <<= amount;
}
static void PQCLEAN_LEDAKEMLT12_CLEAN_gf2x_mul_comb(const int nr, DIGIT Res[],
const int na, const DIGIT A[],
const int nb, const DIGIT B[]) {
int i, j, k;
DIGIT u, h;
memset(Res, 0x00, nr * sizeof(DIGIT));
for (k = DIGIT_SIZE_b - 1; k > 0; k--) {
for (i = na - 1; i >= 0; i--)
if ( A[i] & (((DIGIT)0x1) << k) )
for (j = nb - 1; j >= 0; j--) {
Res[i + j + 1] ^= B[j];
}
u = Res[na + nb - 1];
Res[na + nb - 1] = u << 0x1;
for (j = 1; j < na + nb; ++j) {
h = u >> (DIGIT_SIZE_b - 1);
u = Res[na + nb - 1 - j];
Res[na + nb - 1 - j] = h ^ (u << 0x1);
}
}
for (i = na - 1; i >= 0; i--)
if ( A[i] & ((DIGIT)0x1) )
for (j = nb - 1; j >= 0; j--) {
Res[i + j + 1] ^= B[j];
}
}
static inline void gf2x_exact_div_x_plus_one(const int na, DIGIT A[]) {
DIGIT t = 0;
for (int i = na - 1; i >= 0; i--) {
t ^= A[i];
for (int j = 1; j <= DIGIT_SIZE_b / 2; j = j * 2) {
t ^= t << (unsigned) j;
}
A[i] = t;
t >>= DIGIT_SIZE_b - 1;
}
}
#define MIN_KAR_DIGITS 20
static void PQCLEAN_LEDAKEMLT12_CLEAN_gf2x_mul_Kar(const int nr, DIGIT Res[],
const int na, const DIGIT A[],
const int nb, const DIGIT B[]) {
if (na < MIN_KAR_DIGITS || nb < MIN_KAR_DIGITS) {
/* fall back to schoolbook */
PQCLEAN_LEDAKEMLT12_CLEAN_gf2x_mul_comb(nr, Res, na, A, nb, B);
return;
}
if (na % 2 == 0) {
unsigned bih = na / 2;
DIGIT middle[2 * bih], sumA[bih], sumB[bih];
gf2x_add(sumA, A, A + bih, bih);
gf2x_add(sumB, B, B + bih, bih);
PQCLEAN_LEDAKEMLT12_CLEAN_gf2x_mul_Kar(2 * bih, middle,
bih, sumA,
bih, sumB);
PQCLEAN_LEDAKEMLT12_CLEAN_gf2x_mul_Kar(2 * bih, Res + 2 * bih,
bih, A + bih,
bih, B + bih);
gf2x_add(middle, middle, Res + 2 * bih, 2 * bih);
PQCLEAN_LEDAKEMLT12_CLEAN_gf2x_mul_Kar(2 * bih, Res,
bih, A,
bih, B);
gf2x_add(middle, middle, Res, 2 * bih);
gf2x_add(Res + bih, Res + bih, middle, 2 * bih);
} else {
unsigned bih = na / 2 + 1;
DIGIT middle[2 * bih], sumA[bih], sumB[bih];
gf2x_add_asymm(bih, sumA,
bih, A + bih - 1,
bih - 1, A);
gf2x_add_asymm(bih, sumB,
bih, B + bih - 1,
bih - 1, B);
PQCLEAN_LEDAKEMLT12_CLEAN_gf2x_mul_Kar(2 * bih, middle,
bih, sumA,
bih, sumB);
PQCLEAN_LEDAKEMLT12_CLEAN_gf2x_mul_Kar(2 * bih, Res + 2 * (bih - 1),
bih, A + bih - 1,
bih, B + bih - 1);
gf2x_add(middle, middle, Res + 2 * (bih - 1), 2 * bih);
PQCLEAN_LEDAKEMLT12_CLEAN_gf2x_mul_Kar(2 * (bih - 1), Res,
(bih - 1), A,
(bih - 1), B);
gf2x_add_asymm(2 * bih, middle,
2 * bih, middle,
2 * (bih - 1), Res);
gf2x_add(Res + bih - 2, Res + bih - 2, middle, 2 * bih);
}
}
#define MIN_TOOM_DIGITS 35
void PQCLEAN_LEDAKEMLT12_CLEAN_gf2x_mul_TC3(const int nr, DIGIT Res[],
const int na, const DIGIT A[],
const int nb, const DIGIT B[]) {
if (na < MIN_TOOM_DIGITS || nb < MIN_TOOM_DIGITS) {
/* fall back to Karatsuba */
PQCLEAN_LEDAKEMLT12_CLEAN_gf2x_mul_Kar(nr, Res, na, A, nb, B);
return;
}
unsigned int bih; //number of limbs for each part.
if (na % 3 == 0) {
bih = na / 3;
} else {
bih = na / 3 + 1;
}
DIGIT u2[bih], u1[bih], u0[bih];
unsigned int leading_slack = (3 - (na) % 3) % 3;
// printf("leading slack %d",leading_slack);
unsigned int i;
for (i = 0; i < leading_slack ; i++) {
u2[i] = 0;
}
for (; i < bih; ++i) {
u2[i] = A[i - leading_slack];
}
/* note: only u2 needs to be a copy, refactor */
for (; i < 2 * bih; ++i) {
u1[i - bih] = A[i - leading_slack];
}
for (; i < 3 * bih; ++i) {
u0[i - 2 * bih] = A[i - leading_slack];
}
DIGIT v2[bih], v1[bih], v0[bih]; /* partitioned inputs */
/* note: only v2 needs to be a copy, refactor */
for (i = 0; i < leading_slack ; i++) {
v2[i] = 0;
}
for (; i < bih; ++i) {
v2[i] = B[i - leading_slack];
}
/* note , only v2 needs to be a copy */
for (; i < 2 * bih; ++i) {
v1[i - bih] = B[i - leading_slack];
}
for (; i < 3 * bih; ++i) {
v0[i - 2 * bih] = B[i - leading_slack];
}
DIGIT sum_u[bih]; /*bih digit wide*/
gf2x_add(sum_u, u0, u1, bih);
gf2x_add(sum_u, sum_u, u2, bih);
DIGIT sum_v[bih]; /*bih digit wide*/
gf2x_add(sum_v, v0, v1, bih);
gf2x_add(sum_v, sum_v, v2, bih);
DIGIT w1[2 * bih];
PQCLEAN_LEDAKEMLT12_CLEAN_gf2x_mul_TC3(2 * bih, w1,
bih, sum_u,
bih, sum_v);
DIGIT u2_x2[bih + 1];
u2_x2[0] = 0;
memcpy(u2_x2 + 1, u2, bih * DIGIT_SIZE_B);
PQCLEAN_LEDAKEMLT12_CLEAN_left_bit_shift_n(bih + 1, u2_x2, 2);
DIGIT u1_x[bih + 1];
u1_x[0] = 0;
memcpy(u1_x + 1, u1, bih * DIGIT_SIZE_B);
PQCLEAN_LEDAKEMLT12_CLEAN_left_bit_shift_n(bih + 1, u1_x, 1);
DIGIT u1_x1_u2_x2[bih + 1];
gf2x_add(u1_x1_u2_x2, u1_x, u2_x2, bih + 1);
DIGIT temp_u_components[bih + 1];
gf2x_add_asymm(bih + 1, temp_u_components,
bih + 1, u1_x1_u2_x2,
bih, sum_u);
DIGIT v2_x2[bih + 1];
v2_x2[0] = 0;
memcpy(v2_x2 + 1, v2, bih * DIGIT_SIZE_B);
PQCLEAN_LEDAKEMLT12_CLEAN_left_bit_shift_n(bih + 1, v2_x2, 2);
DIGIT v1_x[bih + 1];
v1_x[0] = 0;
memcpy(v1_x + 1, v1, bih * DIGIT_SIZE_B);
PQCLEAN_LEDAKEMLT12_CLEAN_left_bit_shift_n(bih + 1, v1_x, 1);
DIGIT v1_x1_v2_x2[bih + 1];
gf2x_add(v1_x1_v2_x2, v1_x, v2_x2, bih + 1);
DIGIT temp_v_components[bih + 1];
gf2x_add_asymm(bih + 1, temp_v_components,
bih + 1, v1_x1_v2_x2,
bih, sum_v);
DIGIT w3[2 * bih + 2];
PQCLEAN_LEDAKEMLT12_CLEAN_gf2x_mul_TC3(2 * bih + 2, w3,
bih + 1, temp_u_components,
bih + 1, temp_v_components);
gf2x_add_asymm(bih + 1, u1_x1_u2_x2,
bih + 1, u1_x1_u2_x2,
bih, u0);
gf2x_add_asymm(bih + 1, v1_x1_v2_x2,
bih + 1, v1_x1_v2_x2,
bih, v0);
DIGIT w2[2 * bih + 2];
PQCLEAN_LEDAKEMLT12_CLEAN_gf2x_mul_TC3(2 * bih + 2, w2,
bih + 1, u1_x1_u2_x2,
bih + 1, v1_x1_v2_x2);
DIGIT w4[2 * bih];
PQCLEAN_LEDAKEMLT12_CLEAN_gf2x_mul_TC3(2 * bih, w4,
bih, u2,
bih, v2);
DIGIT w0[2 * bih];
PQCLEAN_LEDAKEMLT12_CLEAN_gf2x_mul_TC3(2 * bih, w0,
bih, u0,
bih, v0);
// Interpolation starts
gf2x_add(w3, w2, w3, 2 * bih + 2);
gf2x_add_asymm(2 * bih + 2, w2,
2 * bih + 2, w2,
2 * bih, w0);
PQCLEAN_LEDAKEMLT12_CLEAN_right_bit_shift_n(2 * bih + 2, w2, 1);
gf2x_add(w2, w2, w3, 2 * bih + 2);
// w2 + (w4 * x^3+1) = w2 + w4 + w4 << 3
DIGIT w4_x3_plus_1[2 * bih + 1];
w4_x3_plus_1[0] = 0;
memcpy(w4_x3_plus_1 + 1, w4, 2 * bih * DIGIT_SIZE_B);
PQCLEAN_LEDAKEMLT12_CLEAN_left_bit_shift_n(2 * bih + 1, w4_x3_plus_1, 3);
gf2x_add_asymm(2 * bih + 2, w2,
2 * bih + 2, w2,
2 * bih, w4);
gf2x_add_asymm(2 * bih + 2, w2,
2 * bih + 2, w2,
2 * bih + 1, w4_x3_plus_1);
gf2x_exact_div_x_plus_one(2 * bih + 2, w2);
gf2x_add(w1, w1, w0, 2 * bih);
gf2x_add_asymm(2 * bih + 2, w3,
2 * bih + 2, w3,
2 * bih, w1);
PQCLEAN_LEDAKEMLT12_CLEAN_right_bit_shift_n(2 * bih + 2, w3, 1);
gf2x_exact_div_x_plus_one(2 * bih + 2, w3);
gf2x_add(w1, w1, w4, 2 * bih);
DIGIT w1_final[2 * bih + 2];
gf2x_add_asymm(2 * bih + 2, w1_final,
2 * bih + 2, w2,
2 * bih, w1);
gf2x_add(w2, w2, w3, 2 * bih + 2);
// Result recombination starts here
memset(Res, 0, nr * DIGIT_SIZE_B);
/* optimization: topmost slack digits should be computed, and not addedd,
* zeroization can be avoided altogether with a proper merge of the
* results */
int leastSignifDigitIdx = nr - 1;
for (int i = 0; i < 2 * bih; i++) {
Res[leastSignifDigitIdx - i] ^= w0[2 * bih - 1 - i];
}
leastSignifDigitIdx -= bih;
for (int i = 0; i < 2 * bih + 2; i++) {
Res[leastSignifDigitIdx - i] ^= w1_final[2 * bih + 2 - 1 - i];
}
leastSignifDigitIdx -= bih;
for (int i = 0; i < 2 * bih + 2; i++) {
Res[leastSignifDigitIdx - i] ^= w2[2 * bih + 2 - 1 - i];
}
leastSignifDigitIdx -= bih;
for (int i = 0; i < 2 * bih + 2 ; i++) {
Res[leastSignifDigitIdx - i] ^= w3[2 * bih + 2 - 1 - i];
}
leastSignifDigitIdx -= bih;
for (int i = 0; i < 2 * bih && (leastSignifDigitIdx - i >= 0) ; i++) {
Res[leastSignifDigitIdx - i] ^= w4[2 * bih - 1 - i];
}
}
// // Unused
// static int gf2x_cmp(const unsigned lenA, const DIGIT A[],
// const unsigned lenB, const DIGIT B[]) {
//
// int i;
// unsigned lA = lenA, lB = lenB;
// for (i = 0; i < lenA && A[i] == 0; i++) {
// lA--;
// }
// for (i = 0; i < lenB && B[i] == 0; i++) {
// lB--;
// }
// if (lA < lB) {
// return -1;
// }
// if (lA > lB) {
// return +1;
// }
// for (i = 0; i < lA; i++) {
// if (A[i] > B[i]) {
// return +1;
// }
// if (A[i] < B[i]) {
// return -1;
// }
// }
// return 0;
//
// }
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