lib/mbedtls
1
0
Fork 0
mirror of https://github.com/Mbed-TLS/mbedtls.git synced 2025-07-29 11:41:15 +03:00
Code Activity

ecp_curves: Minor refactoring of mbedtls_ecp_mod_p255_raw()

Browse Source 
* Fixed whitespace issues.
* Renamed variables to align with bignum conventions.
* Updated alignment on test input data.

Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
This commit is contained in:
Minos Galanakis
2023-05-17 15:01:08 +01:00
parent aada68f1be
commit 2daa374ea8
2 changed files with 32 additions and 52 deletions
Download Patch File Download Diff File Expand all files Collapse all files

24
library/ecp_curves.c
View File

@ -5420,7 +5420,7 @@ int mbedtls_ecp_mod_p521_raw(mbedtls_mpi_uint *X, size_t X_limbs)
static int ecp_mod_p255(mbedtls_mpi *N)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t expected_width = 2 * ((256 + biL - 1) / biL);
size_t expected_width = 2 * ((255 + biL - 1) / biL);
MBEDTLS_MPI_CHK(mbedtls_mpi_grow(N, expected_width));
ret = mbedtls_ecp_mod_p255_raw(N->p, expected_width);
cleanup:
@ -5433,32 +5433,26 @@ int mbedtls_ecp_mod_p255_raw(mbedtls_mpi_uint *X, size_t X_Limbs)
mbedtls_mpi_uint carry[P255_WIDTH];
memset(carry, 0, sizeof(mbedtls_mpi_uint) * P255_WIDTH);
if (X_Limbs > 2*P255_WIDTH) {
X_Limbs = 2*P255_WIDTH;
} else if (X_Limbs < P255_WIDTH) {
return 0;
}
/* Step 1: Reduction to P255_WIDTH limbs */
if (X_Limbs > P255_WIDTH) {
/* Helper references for top part of N */
mbedtls_mpi_uint * const NT_p = X + P255_WIDTH;
const size_t NT_n = X_Limbs - P255_WIDTH;
/* Helper references for top part of X */
mbedtls_mpi_uint * const A1 = X + P255_WIDTH;
const size_t A1_limbs = X_Limbs - P255_WIDTH;
/* N = A0 + 38 * A1, capture carry out */
carry[0] = mbedtls_mpi_core_mla(X, P255_WIDTH, NT_p, NT_n, 38);
/* X = A0 + 38 * A1, capture carry out */
carry[0] = mbedtls_mpi_core_mla(X, P255_WIDTH, A1, A1_limbs, 38);
/* Clear top part */
memset(NT_p, 0, sizeof(mbedtls_mpi_uint) * NT_n);
memset(A1, 0, sizeof(mbedtls_mpi_uint) * A1_limbs);
}
/* Step 2: Reduce to <p
* Split as A0 + 2^255*c, with c a scalar, and compute A0 + 19*c */
carry[0] <<= 1;
carry[0] += (X[P255_WIDTH-1] >> (biL - 1));
carry[0] += (X[P255_WIDTH - 1] >> (biL - 1));
carry[0] *= 19;
/* Clear top bit */
X[P255_WIDTH-1] <<= 1; X[P255_WIDTH-1] >>= 1;
X[P255_WIDTH - 1] <<= 1; X[P255_WIDTH - 1] >>= 1;
(void) mbedtls_mpi_core_add(X, X, &carry[0], P255_WIDTH);
return 0;