yuzu-emu/mbedtls
1
0
Fork 0
mirror of https://github.com/yuzu-emu/mbedtls.git synced 2024-11-22 11:15:43 +01:00
Code Issues Packages Projects Releases Wiki Activity

ECDSA: Fix side channel vulnerability

Browse Source 
The blinding applied to the scalar before modular inversion is
inadequate. Bignum is not constant time/constant trace, side channel
attacks can retrieve the blinded value, factor it (it is smaller than
RSA keys and not guaranteed to have only large prime factors). Then the
key can be recovered by brute force.

Reducing the blinded value makes factoring useless because the adversary
can only recover pk*t+z*N instead of pk*t.
This commit is contained in:
Janos Follath 2019-10-17 10:18:51 +01:00
parent 069fb0e09a
commit d65df1fa67
1 changed files with 1 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
library/ecdsa.c
View File

@ -363,6 +363,7 @@ modn:
MBEDTLS_MPI_CHK( mbedtls_mpi_add_mpi( &e, &e, s ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &e, &e, &t ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( pk, pk, &t ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( pk, pk, &grp->N ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_inv_mod( s, pk, &grp->N ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( s, s, &e ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( s, s, &grp->N ) );