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Use loop for two passes in the reduction

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Signed-off-by: Gabor Mezei <gabor.mezei@arm.com>
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Gabor Mezei 2023-04-14 15:11:14 +02:00
parent 4bf08f86bb
commit f921f4d228
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GPG key ID: FEE76C0CF8C6267D
1 changed files with 22 additions and 47 deletions
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69
library/ecp_curves.c
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@ -5528,7 +5528,6 @@ static inline int ecp_mod_koblitz(mbedtls_mpi *N, mbedtls_mpi_uint *Rp, size_t p
size_t adjust, size_t shift, mbedtls_mpi_uint mask)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t i;
mbedtls_mpi M, R;
mbedtls_mpi_uint Mp[P_KOBLITZ_MAX + P_KOBLITZ_R + 1];
@ -5545,55 +5544,31 @@ static inline int ecp_mod_koblitz(mbedtls_mpi *N, mbedtls_mpi_uint *Rp, size_t p
M.s = 1;
M.p = Mp;
/* M = A1 */
M.n = N->n - (p_limbs - adjust);
if (M.n > p_limbs + adjust) {
M.n = p_limbs + adjust;
}
memset(Mp, 0, sizeof(Mp));
memcpy(Mp, N->p + p_limbs - adjust, M.n * sizeof(mbedtls_mpi_uint));
if (shift != 0) {
MBEDTLS_MPI_CHK(mbedtls_mpi_shift_r(&M, shift));
}
M.n += R.n; /* Make room for multiplication by R */
for (size_t pass = 0; pass < 2; pass++) {
/* M = A1 */
M.n = N->n - (p_limbs - adjust);
if (M.n > p_limbs + adjust) {
M.n = p_limbs + adjust;
}
memset(Mp, 0, sizeof(Mp));
memcpy(Mp, N->p + p_limbs - adjust, M.n * sizeof(mbedtls_mpi_uint));
if (shift != 0) {
MBEDTLS_MPI_CHK(mbedtls_mpi_shift_r(&M, shift));
}
M.n += R.n; /* Make room for multiplication by R */
/* N = A0 */
if (mask != 0) {
N->p[p_limbs - 1] &= mask;
}
for (i = p_limbs; i < N->n; i++) {
N->p[i] = 0;
}
/* N = A0 */
if (mask != 0) {
N->p[p_limbs - 1] &= mask;
}
for (size_t i = p_limbs; i < N->n; i++) {
N->p[i] = 0;
}
/* N = A0 + R * A1 */
MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(&M, &M, &R));
MBEDTLS_MPI_CHK(mbedtls_mpi_add_abs(N, N, &M));
/* Second pass */
/* M = A1 */
M.n = N->n - (p_limbs - adjust);
if (M.n > p_limbs + adjust) {
M.n = p_limbs + adjust;
/* N = A0 + R * A1 */
MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(&M, &M, &R));
MBEDTLS_MPI_CHK(mbedtls_mpi_add_abs(N, N, &M));
}
memset(Mp, 0, sizeof(Mp));
memcpy(Mp, N->p + p_limbs - adjust, M.n * sizeof(mbedtls_mpi_uint));
if (shift != 0) {
MBEDTLS_MPI_CHK(mbedtls_mpi_shift_r(&M, shift));
}
M.n += R.n; /* Make room for multiplication by R */
/* N = A0 */
if (mask != 0) {
N->p[p_limbs - 1] &= mask;
}
for (i = p_limbs; i < N->n; i++) {
N->p[i] = 0;
}
/* N = A0 + R * A1 */
MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(&M, &M, &R));
MBEDTLS_MPI_CHK(mbedtls_mpi_add_abs(N, N, &M));
cleanup:
return ret;