247 lines
8.4 KiB
C
247 lines
8.4 KiB
C
/*************************************************************************************
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* qTESLA: an efficient post-quantum signature scheme based on the R-LWE problem
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*
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* Abstract: NTT, modular reduction and polynomial functions
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**************************************************************************************/
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#include "api.h"
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#include "poly.h"
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#include "sp800-185.h"
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extern const poly PQCLEAN_QTESLAPIII_CLEAN_zeta;
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extern const poly PQCLEAN_QTESLAPIII_CLEAN_zetainv;
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static int64_t reduce(int64_t a) {
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// Montgomery reduction
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int64_t u;
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u = ((uint64_t)a * PARAM_QINV) & 0xFFFFFFFF;
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u *= PARAM_Q;
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a += u;
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return a >> 32;
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}
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static int64_t barr_reduce(int64_t a) {
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// Barrett reduction
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int64_t u = (int64_t)((uint64_t)a * PARAM_BARR_MULT) >> PARAM_BARR_DIV;
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return a - u * PARAM_Q;
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}
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static void ntt(poly a, const poly w) {
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// Forward NTT transform
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size_t NumoProblems = PARAM_N >> 1, jTwiddle = 0;
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for (; NumoProblems > 0; NumoProblems >>= 1) {
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size_t jFirst, j = 0;
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for (jFirst = 0; jFirst < PARAM_N; jFirst = j + NumoProblems) {
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sdigit_t W = (sdigit_t)w[jTwiddle++];
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for (j = jFirst; j < jFirst + NumoProblems; j++) {
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int64_t temp = barr_reduce(reduce((int64_t)W * a[j + NumoProblems]));
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a[j + NumoProblems] = barr_reduce(a[j] + (2LL * PARAM_Q - temp));
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a[j] = barr_reduce(temp + a[j]);
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}
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}
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}
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}
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static void nttinv(poly a, const poly w) {
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// Inverse NTT transform
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size_t NumoProblems = 1, jTwiddle = 0;
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for (; NumoProblems < PARAM_N; NumoProblems *= 2) {
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size_t jFirst, j = 0;
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for (jFirst = 0; jFirst < PARAM_N; jFirst = j + NumoProblems) {
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sdigit_t W = (sdigit_t)w[jTwiddle++];
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for (j = jFirst; j < jFirst + NumoProblems; j++) {
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int64_t temp = a[j];
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a[j] = barr_reduce((temp + a[j + NumoProblems]));
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a[j + NumoProblems] = barr_reduce(reduce((int64_t)W * (temp + (2LL * PARAM_Q - a[j + NumoProblems]))));
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}
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}
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}
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}
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static void poly_pointwise(poly result, const poly x, const poly y) {
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// Pointwise polynomial multiplication result = x.y
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for (size_t i = 0; i < PARAM_N; i++) {
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result[i] = reduce(x[i] * y[i]);
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}
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}
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void PQCLEAN_QTESLAPIII_CLEAN_poly_ntt(poly x_ntt, const poly x) {
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// Call to NTT function. Avoids input destruction
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for (size_t i = 0; i < PARAM_N; i++) {
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x_ntt[i] = x[i];
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}
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ntt(x_ntt, PQCLEAN_QTESLAPIII_CLEAN_zeta);
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}
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void PQCLEAN_QTESLAPIII_CLEAN_poly_mul(poly result, const poly x, const poly y) {
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// Polynomial multiplication result = x*y, with in place reduction for (X^N+1)
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// The inputs x and y are assumed to be in NTT form
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poly_pointwise(result, x, y);
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nttinv(result, PQCLEAN_QTESLAPIII_CLEAN_zetainv);
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}
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void PQCLEAN_QTESLAPIII_CLEAN_poly_add(poly result, const poly x, const poly y) {
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// Polynomial addition result = x+y
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for (size_t i = 0; i < PARAM_N; i++) {
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result[i] = x[i] + y[i];
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}
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}
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void PQCLEAN_QTESLAPIII_CLEAN_poly_add_correct(poly result, const poly x, const poly y) {
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// Polynomial addition result = x+y with correction
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for (size_t i = 0; i < PARAM_N; i++) {
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result[i] = x[i] + y[i];
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result[i] -= PARAM_Q;
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result[i] += (result[i] >> (RADIX32 - 1)) & PARAM_Q; // If result[i] >= q then subtract q
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}
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}
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void PQCLEAN_QTESLAPIII_CLEAN_poly_sub(poly result, const poly x, const poly y) {
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// Polynomial subtraction result = x-y
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for (size_t i = 0; i < PARAM_N; i++) {
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result[i] = barr_reduce(x[i] - y[i]);
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}
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}
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/********************************************************************************************
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* Name: sparse_mul8
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* Description: performs sparse polynomial multiplication
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* Parameters: inputs:
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* - const uint8_t *s: part of the secret key
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* - const uint32_t pos_list[PARAM_H]: list of indices of nonzero elements in c
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* - const int16_t sign_list[PARAM_H]: list of signs of nonzero elements in c
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* outputs:
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* - poly prod: product of 2 polynomials
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*
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* Note: pos_list[] and sign_list[] contain public information since c is public
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*********************************************************************************************/
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void PQCLEAN_QTESLAPIII_CLEAN_sparse_mul8(poly prod, const uint8_t *s, const uint32_t pos_list[PARAM_H], const int16_t sign_list[PARAM_H]) {
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size_t i, j, pos;
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int8_t *t = (int8_t *)s;
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for (i = 0; i < PARAM_N; i++) {
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prod[i] = 0;
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}
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for (i = 0; i < PARAM_H; i++) {
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pos = pos_list[i];
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for (j = 0; j < pos; j++) {
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prod[j] = prod[j] - sign_list[i] * t[j + PARAM_N - pos];
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}
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for (j = pos; j < PARAM_N; j++) {
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prod[j] = prod[j] + sign_list[i] * t[j - pos];
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}
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}
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}
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/********************************************************************************************
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* Name: sparse_mul32
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* Description: performs sparse polynomial multiplication
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* Parameters: inputs:
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* - const int32_t* pk: part of the public key
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* - const uint32_t pos_list[PARAM_H]: list of indices of nonzero elements in c
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* - const int16_t sign_list[PARAM_H]: list of signs of nonzero elements in c
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* outputs:
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* - poly prod: product of 2 polynomials
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*********************************************************************************************/
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void PQCLEAN_QTESLAPIII_CLEAN_sparse_mul32(poly prod, const int32_t *pk, const uint32_t pos_list[PARAM_H], const int16_t sign_list[PARAM_H]) {
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size_t i, j, pos;
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for (i = 0; i < PARAM_N; i++) {
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prod[i] = 0;
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}
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for (i = 0; i < PARAM_H; i++) {
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pos = pos_list[i];
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for (j = 0; j < pos; j++) {
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prod[j] = prod[j] - sign_list[i] * pk[j + PARAM_N - pos];
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}
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for (j = pos; j < PARAM_N; j++) {
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prod[j] = prod[j] + sign_list[i] * pk[j - pos];
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}
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}
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for (i = 0; i < PARAM_N; i++) {
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prod[i] = barr_reduce(prod[i]);
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}
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}
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void PQCLEAN_QTESLAPIII_CLEAN_poly_uniform(poly_k a, const uint8_t *seed) {
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// Generation of polynomials "a_i"
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size_t pos = 0, i = 0, nbytes = (PARAM_Q_LOG + 7) / 8;
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size_t nblocks = PARAM_GEN_A;
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uint32_t val1, val2, val3, val4, mask = (uint32_t)(1 << PARAM_Q_LOG) - 1;
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uint8_t buf[SHAKE128_RATE * PARAM_GEN_A];
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uint16_t dmsp = 0;
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uint8_t dmsp_bytes[2];
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dmsp_bytes[0] = (uint8_t)(dmsp & 0xff);
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dmsp_bytes[1] = (uint8_t)(dmsp >> 8);
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cshake128(buf, SHAKE128_RATE * PARAM_GEN_A, (uint8_t *)NULL, 0, dmsp_bytes, 2, seed, CRYPTO_RANDOMBYTES);
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++dmsp;
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while (i < PARAM_K * PARAM_N) {
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if (pos > SHAKE128_RATE * nblocks - 4 * nbytes) {
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nblocks = 1;
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dmsp_bytes[0] = (uint8_t)(dmsp & 0xff);
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dmsp_bytes[1] = (uint8_t)(dmsp >> 8);
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cshake128(buf, SHAKE128_RATE * nblocks, (uint8_t *)NULL, 0, dmsp_bytes, 2, seed, CRYPTO_RANDOMBYTES);
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++dmsp;
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pos = 0;
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}
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val1 = ((uint32_t)(buf[pos])
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| ((uint32_t)buf[pos + 1] << 8)
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| ((uint32_t)buf[pos + 2] << 16)
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| ((uint32_t)buf[pos + 3] << 24))
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& mask;
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pos += nbytes;
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val2 = ((uint32_t)(buf[pos])
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| ((uint32_t)buf[pos + 1] << 8)
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| ((uint32_t)buf[pos + 2] << 16)
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| ((uint32_t)buf[pos + 3] << 24))
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& mask;
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pos += nbytes;
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val3 = ((uint32_t)(buf[pos])
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| ((uint32_t)buf[pos + 1] << 8)
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| ((uint32_t)buf[pos + 2] << 16)
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| ((uint32_t)buf[pos + 3] << 24))
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& mask;
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pos += nbytes;
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val4 = ((uint32_t)(buf[pos])
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| ((uint32_t)buf[pos + 1] << 8)
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| ((uint32_t)buf[pos + 2] << 16)
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| ((uint32_t)buf[pos + 3] << 24))
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& mask;
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pos += nbytes;
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if (val1 < PARAM_Q && i < PARAM_K * PARAM_N) {
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a[i++] = reduce((int64_t)val1 * PARAM_R2_INVN);
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}
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if (val2 < PARAM_Q && i < PARAM_K * PARAM_N) {
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a[i++] = reduce((int64_t)val2 * PARAM_R2_INVN);
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}
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if (val3 < PARAM_Q && i < PARAM_K * PARAM_N) {
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a[i++] = reduce((int64_t)val3 * PARAM_R2_INVN);
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}
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if (val4 < PARAM_Q && i < PARAM_K * PARAM_N) {
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a[i++] = reduce((int64_t)val4 * PARAM_R2_INVN);
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}
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}
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}
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