mirror/mbedtls
1
0
Fork 0
mirror of https://github.com/Mbed-TLS/mbedtls.git synced 2025-03-16 04:20:49 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

Use actual exponent size for window calculation

Browse Source 
The allocated size can be significantly larger than the actual size. In
the unsafe case we can use the actual size and gain some performance.

Signed-off-by: Janos Follath <janos.follath@arm.com>
This commit is contained in:
Janos Follath 2024-08-13 07:53:20 +01:00 committed by Manuel Pégourié-Gonnard
parent 8fc736dc4e
commit a099ac9812
1 changed files with 9 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
tf-psa-crypto/drivers/builtin/src/bignum_core.c
View File

@ -822,7 +822,15 @@ static void mbedtls_mpi_core_exp_mod_optionally_safe(mbedtls_mpi_uint *X,
const mbedtls_mpi_uint *RR,
mbedtls_mpi_uint *T)
{
const size_t wsize = exp_mod_get_window_size(E_limbs * biL);
/* We'll process the bits of E from most significant
* (limb_index=E_limbs-1, E_bit_index=biL-1) to least significant
* (limb_index=0, E_bit_index=0). */
size_t E_limb_index = E_limbs;
size_t E_bit_index = 0;
exp_mod_calc_first_bit_optionally_safe(E, E_limbs, E_public,
&E_limb_index, &E_bit_index);
const size_t wsize = exp_mod_get_window_size(E_limb_index * biL);
const size_t welem = ((size_t) 1) << wsize;
/* This is how we will use the temporary storage T, which must have space
@ -853,14 +861,6 @@ static void mbedtls_mpi_core_exp_mod_optionally_safe(mbedtls_mpi_uint *X,
/* X = 1 (in Montgomery presentation) initially */
memcpy(X, Wtable, AN_limbs * ciL);
/* We'll process the bits of E from most significant
* (limb_index=E_limbs-1, E_bit_index=biL-1) to least significant
* (limb_index=0, E_bit_index=0). */
size_t E_limb_index = E_limbs;
size_t E_bit_index = 0;
exp_mod_calc_first_bit_optionally_safe(E, E_limbs, E_public,
&E_limb_index, &E_bit_index);
/* At any given time, window contains window_bits bits from E.
* window_bits can go up to wsize. */
size_t window_bits = 0;