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pqcrypto/crypto_kem/saber/clean/poly_mul.c
Sofía Celi c59580a355 Fix overflow in multiplication in Saber
2021-03-24 21:02:46 +00:00

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#include "poly_mul.h"
#include <stdint.h>
#include <string.h>
#define SCHB_N 16
#define N_RES (SABER_N << 1)
#define N_SB (SABER_N >> 2)
#define N_SB_RES (2*N_SB-1)
#define OVERFLOWING_MUL(X, Y) ((uint16_t)((uint32_t)(X) * (uint32_t)(Y)))
#define KARATSUBA_N 64
static void karatsuba_simple(const uint16_t *a_1, const uint16_t *b_1, uint16_t *result_final) {
uint16_t d01[KARATSUBA_N / 2 - 1];
uint16_t d0123[KARATSUBA_N / 2 - 1];
uint16_t d23[KARATSUBA_N / 2 - 1];
uint16_t result_d01[KARATSUBA_N - 1];
int32_t i, j;
memset(result_d01, 0, (KARATSUBA_N - 1)*sizeof(uint16_t));
memset(d01, 0, (KARATSUBA_N / 2 - 1)*sizeof(uint16_t));
memset(d0123, 0, (KARATSUBA_N / 2 - 1)*sizeof(uint16_t));
memset(d23, 0, (KARATSUBA_N / 2 - 1)*sizeof(uint16_t));
memset(result_final, 0, (2 * KARATSUBA_N - 1)*sizeof(uint16_t));
uint16_t acc1, acc2, acc3, acc4, acc5, acc6, acc7, acc8, acc9, acc10;
for (i = 0; i < KARATSUBA_N / 4; i++) {
acc1 = a_1[i]; //a0
acc2 = a_1[i + KARATSUBA_N / 4]; //a1
acc3 = a_1[i + 2 * KARATSUBA_N / 4]; //a2
acc4 = a_1[i + 3 * KARATSUBA_N / 4]; //a3
for (j = 0; j < KARATSUBA_N / 4; j++) {
acc5 = b_1[j]; //b0
acc6 = b_1[j + KARATSUBA_N / 4]; //b1
result_final[i + j + 0 * KARATSUBA_N / 4] =
result_final[i + j + 0 * KARATSUBA_N / 4] +
OVERFLOWING_MUL(acc1, acc5);
result_final[i + j + 2 * KARATSUBA_N / 4] =
result_final[i + j + 2 * KARATSUBA_N / 4] +
OVERFLOWING_MUL(acc2, acc6);
acc7 = acc5 + acc6; //b01
acc8 = acc1 + acc2; //a01
d01[i + j] = d01[i + j] + (uint16_t)(acc7 * (uint64_t)acc8);
//--------------------------------------------------------
acc7 = b_1[j + 2 * KARATSUBA_N / 4]; //b2
acc8 = b_1[j + 3 * KARATSUBA_N / 4]; //b3
result_final[i + j + 4 * KARATSUBA_N / 4] =
result_final[i + j + 4 * KARATSUBA_N / 4] +
OVERFLOWING_MUL(acc7, acc3);
result_final[i + j + 6 * KARATSUBA_N / 4] =
result_final[i + j + 6 * KARATSUBA_N / 4] +
OVERFLOWING_MUL(acc8, acc4);
acc9 = acc3 + acc4;
acc10 = acc7 + acc8;
d23[i + j] = d23[i + j] + OVERFLOWING_MUL(acc9, acc10);
//--------------------------------------------------------
acc5 = acc5 + acc7; //b02
acc7 = acc1 + acc3; //a02
result_d01[i + j + 0 * KARATSUBA_N / 4] =
result_d01[i + j + 0 * KARATSUBA_N / 4] +
OVERFLOWING_MUL(acc5, acc7);
acc6 = acc6 + acc8; //b13
acc8 = acc2 + acc4;
result_d01[i + j + 2 * KARATSUBA_N / 4] =
result_d01[i + j + 2 * KARATSUBA_N / 4] +
OVERFLOWING_MUL(acc6, acc8);
acc5 = acc5 + acc6;
acc7 = acc7 + acc8;
d0123[i + j] = d0123[i + j] + OVERFLOWING_MUL(acc5, acc7);
}
}
// 2nd last stage
for (i = 0; i < KARATSUBA_N / 2 - 1; i++) {
d0123[i] = d0123[i] - result_d01[i + 0 * KARATSUBA_N / 4] - result_d01[i + 2 * KARATSUBA_N / 4];
d01[i] = d01[i] - result_final[i + 0 * KARATSUBA_N / 4] - result_final[i + 2 * KARATSUBA_N / 4];
d23[i] = d23[i] - result_final[i + 4 * KARATSUBA_N / 4] - result_final[i + 6 * KARATSUBA_N / 4];
}
for (i = 0; i < KARATSUBA_N / 2 - 1; i++) {
result_d01[i + 1 * KARATSUBA_N / 4] = result_d01[i + 1 * KARATSUBA_N / 4] + d0123[i];
result_final[i + 1 * KARATSUBA_N / 4] = result_final[i + 1 * KARATSUBA_N / 4] + d01[i];
result_final[i + 5 * KARATSUBA_N / 4] = result_final[i + 5 * KARATSUBA_N / 4] + d23[i];
}
// Last stage
for (i = 0; i < KARATSUBA_N - 1; i++) {
result_d01[i] = result_d01[i] - result_final[i] - result_final[i + KARATSUBA_N];
}
for (i = 0; i < KARATSUBA_N - 1; i++) {
result_final[i + 1 * KARATSUBA_N / 2] = result_final[i + 1 * KARATSUBA_N / 2] + result_d01[i];
}
}
static void toom_cook_4way (const uint16_t *a1, const uint16_t *b1, uint16_t *result) {
uint16_t inv3 = 43691, inv9 = 36409, inv15 = 61167;
uint16_t aw1[N_SB], aw2[N_SB], aw3[N_SB], aw4[N_SB], aw5[N_SB], aw6[N_SB], aw7[N_SB];
uint16_t bw1[N_SB], bw2[N_SB], bw3[N_SB], bw4[N_SB], bw5[N_SB], bw6[N_SB], bw7[N_SB];
uint16_t w1[N_SB_RES] = {0}, w2[N_SB_RES] = {0}, w3[N_SB_RES] = {0}, w4[N_SB_RES] = {0},
w5[N_SB_RES] = {0}, w6[N_SB_RES] = {0}, w7[N_SB_RES] = {0};
uint16_t r0, r1, r2, r3, r4, r5, r6, r7;
uint16_t *A0, *A1, *A2, *A3, *B0, *B1, *B2, *B3;
A0 = (uint16_t *)a1;
A1 = (uint16_t *)&a1[N_SB];
A2 = (uint16_t *)&a1[2 * N_SB];
A3 = (uint16_t *)&a1[3 * N_SB];
B0 = (uint16_t *)b1;
B1 = (uint16_t *)&b1[N_SB];
B2 = (uint16_t *)&b1[2 * N_SB];
B3 = (uint16_t *)&b1[3 * N_SB];
uint16_t *C;
C = result;
int i, j;
// EVALUATION
for (j = 0; j < N_SB; ++j) {
r0 = A0[j];
r1 = A1[j];
r2 = A2[j];
r3 = A3[j];
r4 = r0 + r2;
r5 = r1 + r3;
r6 = r4 + r5;
r7 = r4 - r5;
aw3[j] = r6;
aw4[j] = r7;
r4 = ((r0 << 2) + r2) << 1;
r5 = (r1 << 2) + r3;
r6 = r4 + r5;
r7 = r4 - r5;
aw5[j] = r6;
aw6[j] = r7;
r4 = (r3 << 3) + (r2 << 2) + (r1 << 1) + r0;
aw2[j] = r4;
aw7[j] = r0;
aw1[j] = r3;
}
for (j = 0; j < N_SB; ++j) {
r0 = B0[j];
r1 = B1[j];
r2 = B2[j];
r3 = B3[j];
r4 = r0 + r2;
r5 = r1 + r3;
r6 = r4 + r5;
r7 = r4 - r5;
bw3[j] = r6;
bw4[j] = r7;
r4 = ((r0 << 2) + r2) << 1;
r5 = (r1 << 2) + r3;
r6 = r4 + r5;
r7 = r4 - r5;
bw5[j] = r6;
bw6[j] = r7;
r4 = (r3 << 3) + (r2 << 2) + (r1 << 1) + r0;
bw2[j] = r4;
bw7[j] = r0;
bw1[j] = r3;
}
// MULTIPLICATION
karatsuba_simple(aw1, bw1, w1);
karatsuba_simple(aw2, bw2, w2);
karatsuba_simple(aw3, bw3, w3);
karatsuba_simple(aw4, bw4, w4);
karatsuba_simple(aw5, bw5, w5);
karatsuba_simple(aw6, bw6, w6);
karatsuba_simple(aw7, bw7, w7);
// INTERPOLATION
for (i = 0; i < N_SB_RES; ++i) {
r0 = w1[i];
r1 = w2[i];
r2 = w3[i];
r3 = w4[i];
r4 = w5[i];
r5 = w6[i];
r6 = w7[i];
r1 = r1 + r4;
r5 = r5 - r4;
r3 = ((r3 - r2) >> 1);
r4 = r4 - r0;
r4 = r4 - (r6 << 6);
r4 = (r4 << 1) + r5;
r2 = r2 + r3;
r1 = r1 - (r2 << 6) - r2;
r2 = r2 - r6;
r2 = r2 - r0;
r1 = r1 + 45 * r2;
r4 = (uint16_t)(((r4 - (r2 << 3)) * (uint32_t)inv3) >> 3);
r5 = r5 + r1;
r1 = (uint16_t)(((r1 + (r3 << 4)) * (uint32_t)inv9) >> 1);
r3 = -(r3 + r1);
r5 = (uint16_t)(((30 * r1 - r5) * (uint32_t)inv15) >> 2);
r2 = r2 - r4;
r1 = r1 - r5;
C[i] += r6;
C[i + 64] += r5;
C[i + 128] += r4;
C[i + 192] += r3;
C[i + 256] += r2;
C[i + 320] += r1;
C[i + 384] += r0;
}
}
void PQCLEAN_SABER_CLEAN_pol_mul(uint16_t *a, uint16_t *b, uint16_t *res, uint16_t p, uint32_t n) {
uint32_t i;
// normal multiplication
uint16_t c[512];
for (i = 0; i < 512; i++) {
c[i] = 0;
}
toom_cook_4way(a, b, c);
// reduction
for (i = n; i < 2 * n; i++) {
res[i - n] = (c[i - n] - c[i]) & (p - 1);
}
}
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