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82fdce64a2
pqcrypto/crypto_kem/newhope1024cca/clean/poly.c
Douglas Stebila 82fdce64a2 Macro for loop length
2019-05-18 11:27:45 +02:00

358 lines
13 KiB
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#include "fips202.h"
#include "ntt.h"
#include "poly.h"
#include "reduce.h"
/*************************************************
* Name: coeff_freeze
*
* Description: Fully reduces an integer modulo q in constant time
*
* Arguments: uint16_t x: input integer to be reduced
*
* Returns integer in {0,...,q-1} congruent to x modulo q
**************************************************/
static uint16_t coeff_freeze(uint16_t x) {
uint16_t m, r;
int16_t c;
r = x % NEWHOPE_Q;
m = r - NEWHOPE_Q;
c = m;
c >>= 15;
r = m ^ ((r ^ m)&c);
return r;
}
/*************************************************
* Name: flipabs
*
* Description: Computes |(x mod q) - Q/2|
*
* Arguments: uint16_t x: input coefficient
*
* Returns |(x mod q) - Q/2|
**************************************************/
static uint16_t flipabs(uint16_t x) {
int16_t r, m;
r = coeff_freeze(x);
r = r - NEWHOPE_Q / 2;
m = r >> 15;
return (r + m) ^ m;
}
/*************************************************
* Name: poly_frombytes
*
* Description: De-serialization of a polynomial
*
* Arguments: - poly *r: pointer to output polynomial
* - const unsigned char *a: pointer to input byte array
**************************************************/
void PQCLEAN_NEWHOPE1024CCA_CLEAN_poly_frombytes(poly *r, const unsigned char *a) {
int i;
for (i = 0; i < NEWHOPE_N / 4; i++) {
r->coeffs[4 * i + 0] = a[7 * i + 0] | (((uint16_t)a[7 * i + 1] & 0x3f) << 8);
r->coeffs[4 * i + 1] = (a[7 * i + 1] >> 6) | (((uint16_t)a[7 * i + 2]) << 2) | (((uint16_t)a[7 * i + 3] & 0x0f) << 10);
r->coeffs[4 * i + 2] = (a[7 * i + 3] >> 4) | (((uint16_t)a[7 * i + 4]) << 4) | (((uint16_t)a[7 * i + 5] & 0x03) << 12);
r->coeffs[4 * i + 3] = (a[7 * i + 5] >> 2) | (((uint16_t)a[7 * i + 6]) << 6);
}
}
/*************************************************
* Name: poly_tobytes
*
* Description: Serialization of a polynomial
*
* Arguments: - unsigned char *r: pointer to output byte array
* - const poly *p: pointer to input polynomial
**************************************************/
void PQCLEAN_NEWHOPE1024CCA_CLEAN_poly_tobytes(unsigned char *r, const poly *p) {
int i;
uint16_t t0, t1, t2, t3;
for (i = 0; i < NEWHOPE_N / 4; i++) {
t0 = coeff_freeze(p->coeffs[4 * i + 0]);
t1 = coeff_freeze(p->coeffs[4 * i + 1]);
t2 = coeff_freeze(p->coeffs[4 * i + 2]);
t3 = coeff_freeze(p->coeffs[4 * i + 3]);
r[7 * i + 0] = t0 & 0xff;
r[7 * i + 1] = (unsigned char) ((t0 >> 8) | (t1 << 6));
r[7 * i + 2] = (unsigned char) ((t1 >> 2));
r[7 * i + 3] = (unsigned char) ((t1 >> 10) | (t2 << 4));
r[7 * i + 4] = (unsigned char) ((t2 >> 4));
r[7 * i + 5] = (unsigned char) ((t2 >> 12) | (t3 << 2));
r[7 * i + 6] = (unsigned char) ((t3 >> 6));
}
}
/*************************************************
* Name: poly_compress
*
* Description: Compression and subsequent serialization of a polynomial
*
* Arguments: - unsigned char *r: pointer to output byte array
* - const poly *p: pointer to input polynomial
**************************************************/
void PQCLEAN_NEWHOPE1024CCA_CLEAN_poly_compress(unsigned char *r, const poly *p) {
unsigned int i, j, k = 0;
uint32_t t[8];
for (i = 0; i < NEWHOPE_N; i += 8) {
for (j = 0; j < 8; j++) {
t[j] = coeff_freeze(p->coeffs[i + j]);
t[j] = (((t[j] << 3) + NEWHOPE_Q / 2) / NEWHOPE_Q) & 0x7;
}
r[k] = (unsigned char) (t[0] | (t[1] << 3) | (t[2] << 6));
r[k + 1] = (unsigned char) ((t[2] >> 2) | (t[3] << 1) | (t[4] << 4) | (t[5] << 7));
r[k + 2] = (unsigned char) ((t[5] >> 1) | (t[6] << 2) | (t[7] << 5));
k += 3;
}
}
/*************************************************
* Name: poly_decompress
*
* Description: De-serialization and subsequent decompression of a polynomial;
* approximate inverse of poly_compress
*
* Arguments: - poly *r: pointer to output polynomial
* - const unsigned char *a: pointer to input byte array
**************************************************/
void PQCLEAN_NEWHOPE1024CCA_CLEAN_poly_decompress(poly *r, const unsigned char *a) {
unsigned int i, j;
for (i = 0; i < NEWHOPE_N; i += 8) {
r->coeffs[i + 0] = a[0] & 7;
r->coeffs[i + 1] = (a[0] >> 3) & 7;
r->coeffs[i + 2] = (a[0] >> 6) | ((a[1] << 2) & 4);
r->coeffs[i + 3] = (a[1] >> 1) & 7;
r->coeffs[i + 4] = (a[1] >> 4) & 7;
r->coeffs[i + 5] = (a[1] >> 7) | ((a[2] << 1) & 6);
r->coeffs[i + 6] = (a[2] >> 2) & 7;
r->coeffs[i + 7] = (a[2] >> 5);
a += 3;
for (j = 0; j < 8; j++) {
r->coeffs[i + j] = ((uint32_t)r->coeffs[i + j] * NEWHOPE_Q + 4) >> 3;
}
}
}
/*************************************************
* Name: poly_frommsg
*
* Description: Convert 32-byte message to polynomial
*
* Arguments: - poly *r: pointer to output polynomial
* - const unsigned char *msg: pointer to input message
**************************************************/
void PQCLEAN_NEWHOPE1024CCA_CLEAN_poly_frommsg(poly *r, const unsigned char *msg) {
unsigned int i, j, mask;
for (i = 0; i < NEWHOPE_SYMBYTES; i++) {
for (j = 0; j < 8; j++) {
mask = -((msg[i] >> j) & 1);
r->coeffs[8 * i + j + 0] = mask & (NEWHOPE_Q / 2);
r->coeffs[8 * i + j + 256] = mask & (NEWHOPE_Q / 2);
r->coeffs[8 * i + j + 512] = mask & (NEWHOPE_Q / 2);
r->coeffs[8 * i + j + 768] = mask & (NEWHOPE_Q / 2);
}
}
}
/*************************************************
* Name: poly_tomsg
*
* Description: Convert polynomial to 32-byte message
*
* Arguments: - unsigned char *msg: pointer to output message
* - const poly *x: pointer to input polynomial
**************************************************/
void PQCLEAN_NEWHOPE1024CCA_CLEAN_poly_tomsg(unsigned char *msg, const poly *x) {
unsigned int i;
uint16_t t;
for (i = 0; i < 32; i++) {
msg[i] = 0;
}
for (i = 0; i < 256; i++) {
t = flipabs(x->coeffs[i + 0]);
t += flipabs(x->coeffs[i + 256]);
t += flipabs(x->coeffs[i + 512]);
t += flipabs(x->coeffs[i + 768]);
t = ((t - NEWHOPE_Q));
t >>= 15;
msg[i >> 3] |= t << (i & 7);
}
}
/*************************************************
* Name: poly_uniform
*
* Description: Sample a polynomial deterministically from a seed,
* with output polynomial looking uniformly random
*
* Arguments: - poly *a: pointer to output polynomial
* - const unsigned char *seed: pointer to input seed
**************************************************/
void PQCLEAN_NEWHOPE1024CCA_CLEAN_poly_uniform(poly *a, const unsigned char *seed) {
unsigned int ctr = 0;
uint16_t val;
uint64_t state[25];
uint8_t buf[SHAKE128_RATE];
uint8_t extseed[NEWHOPE_SYMBYTES + 1];
int i, j;
for (i = 0; i < NEWHOPE_SYMBYTES; i++) {
extseed[i] = seed[i];
}
for (i = 0; i < NEWHOPE_N / 64; i++) { /* generate a in blocks of 64 coefficients */
ctr = 0;
extseed[NEWHOPE_SYMBYTES] = (unsigned char) i; /* domain-separate the 16 independent calls */
shake128_absorb(state, extseed, NEWHOPE_SYMBYTES + 1);
while (ctr < 64) { /* Very unlikely to run more than once */
shake128_squeezeblocks(buf, 1, state);
for (j = 0; j < SHAKE128_RATE && ctr < 64; j += 2) {
val = (buf[j] | ((uint16_t) buf[j + 1] << 8));
if (val < 5 * NEWHOPE_Q) {
a->coeffs[i * 64 + ctr] = val;
ctr++;
}
}
}
}
}
/*************************************************
* Name: hw
*
* Description: Compute the Hamming weight of a byte
*
* Arguments: - unsigned char a: input byte
**************************************************/
static unsigned char hw(unsigned char a) {
unsigned char i, r = 0;
for (i = 0; i < 8; i++) {
r += (a >> i) & 1;
}
return r;
}
/*************************************************
* Name: poly_sample
*
* Description: Sample a polynomial deterministically from a seed and a nonce,
* with output polynomial close to centered binomial distribution
* with parameter k=8
*
* Arguments: - poly *r: pointer to output polynomial
* - const unsigned char *seed: pointer to input seed
* - unsigned char nonce: one-byte input nonce
**************************************************/
void PQCLEAN_NEWHOPE1024CCA_CLEAN_poly_sample(poly *r, const unsigned char *seed, unsigned char nonce) {
unsigned char buf[128], a, b;
int i, j;
unsigned char extseed[NEWHOPE_SYMBYTES + 2];
for (i = 0; i < NEWHOPE_SYMBYTES; i++) {
extseed[i] = seed[i];
}
extseed[NEWHOPE_SYMBYTES] = nonce;
for (i = 0; i < NEWHOPE_N / 64; i++) { /* Generate noise in blocks of 64 coefficients */
extseed[NEWHOPE_SYMBYTES + 1] = (unsigned char) i;
shake256(buf, 128, extseed, NEWHOPE_SYMBYTES + 2);
for (j = 0; j < 64; j++) {
a = buf[2 * j];
b = buf[2 * j + 1];
r->coeffs[64 * i + j] = hw(a) + NEWHOPE_Q - hw(b);
}
}
}
/*************************************************
* Name: poly_pointwise
*
* Description: Multiply two polynomials pointwise (i.e., coefficient-wise).
*
* Arguments: - poly *r: pointer to output polynomial
* - const poly *a: pointer to first input polynomial
* - const poly *b: pointer to second input polynomial
**************************************************/
void PQCLEAN_NEWHOPE1024CCA_CLEAN_poly_mul_pointwise(poly *r, const poly *a, const poly *b) {
int i;
uint16_t t;
for (i = 0; i < NEWHOPE_N; i++) {
t = PQCLEAN_NEWHOPE1024CCA_CLEAN_montgomery_reduce(3186 * b->coeffs[i]); /* t is now in Montgomery domain */
r->coeffs[i] = PQCLEAN_NEWHOPE1024CCA_CLEAN_montgomery_reduce(a->coeffs[i] * t); /* r->coeffs[i] is back in normal domain */
}
}
/*************************************************
* Name: poly_add
*
* Description: Add two polynomials
*
* Arguments: - poly *r: pointer to output polynomial
* - const poly *a: pointer to first input polynomial
* - const poly *b: pointer to second input polynomial
**************************************************/
void PQCLEAN_NEWHOPE1024CCA_CLEAN_poly_add(poly *r, const poly *a, const poly *b) {
int i;
for (i = 0; i < NEWHOPE_N; i++) {
r->coeffs[i] = (a->coeffs[i] + b->coeffs[i]) % NEWHOPE_Q;
}
}
/*************************************************
* Name: poly_sub
*
* Description: Subtract two polynomials
*
* Arguments: - poly *r: pointer to output polynomial
* - const poly *a: pointer to first input polynomial
* - const poly *b: pointer to second input polynomial
**************************************************/
void PQCLEAN_NEWHOPE1024CCA_CLEAN_poly_sub(poly *r, const poly *a, const poly *b) {
int i;
for (i = 0; i < NEWHOPE_N; i++) {
r->coeffs[i] = (a->coeffs[i] + 3 * NEWHOPE_Q - b->coeffs[i]) % NEWHOPE_Q;
}
}
/*************************************************
* Name: poly_ntt
*
* Description: Forward NTT transform of a polynomial in place
* Input is assumed to have coefficients in bitreversed order
* Output has coefficients in normal order
*
* Arguments: - poly *r: pointer to in/output polynomial
**************************************************/
void PQCLEAN_NEWHOPE1024CCA_CLEAN_poly_ntt(poly *r) {
PQCLEAN_NEWHOPE1024CCA_CLEAN_mul_coefficients(r->coeffs, PQCLEAN_NEWHOPE1024CCA_CLEAN_gammas_bitrev_montgomery);
PQCLEAN_NEWHOPE1024CCA_CLEAN_ntt((uint16_t *)r->coeffs, PQCLEAN_NEWHOPE1024CCA_CLEAN_gammas_bitrev_montgomery);
}
/*************************************************
* Name: poly_invntt
*
* Description: Inverse NTT transform of a polynomial in place
* Input is assumed to have coefficients in normal order
* Output has coefficients in normal order
*
* Arguments: - poly *r: pointer to in/output polynomial
**************************************************/
void PQCLEAN_NEWHOPE1024CCA_CLEAN_poly_invntt(poly *r) {
PQCLEAN_NEWHOPE1024CCA_CLEAN_bitrev_vector(r->coeffs);
PQCLEAN_NEWHOPE1024CCA_CLEAN_ntt((uint16_t *)r->coeffs, PQCLEAN_NEWHOPE1024CCA_CLEAN_omegas_inv_bitrev_montgomery);
PQCLEAN_NEWHOPE1024CCA_CLEAN_mul_coefficients(r->coeffs, PQCLEAN_NEWHOPE1024CCA_CLEAN_gammas_inv_montgomery);
}
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