diff --git a/cipher/rsa.c b/cipher/rsa.c --- a/cipher/rsa.c +++ b/cipher/rsa.c @@ -29,6 +29,7 @@ #include #include "util.h" #include "mpi.h" +#include "../mpi/mpi-internal.h" #include "cipher.h" #include "rsa.h" @@ -325,14 +326,38 @@ # endif /* USE_BLINDING */ /* RSA secret operation: */ - /* m1 = c ^ (d mod (p-1)) mod p */ + MPI D_blind = mpi_alloc_secure (nlimbs); + MPI rr; + unsigned int rr_nbits; + + rr_nbits = mpi_get_nbits (skey->p) / 4; + if (rr_nbits < 96) + rr_nbits = 96; + rr = mpi_alloc_secure ( (rr_nbits + BITS_PER_MPI_LIMB-1)/BITS_PER_MPI_LIMB ); + + /* d_blind = (d mod (p-1)) + (p-1) * r */ + /* m1 = c ^ d_blind mod p */ + randomize_mpi (rr, rr_nbits, 0); + mpi_set_highbit (rr, rr_nbits - 1); mpi_sub_ui( h, skey->p, 1 ); + mpi_mul ( D_blind, h, rr ); mpi_fdiv_r( h, skey->d, h ); - mpi_powm( m1, input, h, skey->p ); - /* m2 = c ^ (d mod (q-1)) mod q */ + mpi_add ( D_blind, D_blind, h ); + mpi_powm ( m1, input, D_blind, skey->p ); + + /* d_blind = (d mod (q-1)) + (q-1) * r */ + /* m2 = c ^ d_blind mod q */ + randomize_mpi (rr, rr_nbits, 0); + mpi_set_highbit (rr, rr_nbits - 1); mpi_sub_ui( h, skey->q, 1 ); + mpi_mul ( D_blind, h, rr ); mpi_fdiv_r( h, skey->d, h ); - mpi_powm( m2, input, h, skey->q ); + mpi_add ( D_blind, D_blind, h ); + mpi_powm ( m2, input, D_blind, skey->q ); + + mpi_free ( rr ); + mpi_free ( D_blind ); + /* h = u * ( m2 - m1 ) mod q */ mpi_sub( h, m2, m1 ); if ( mpi_is_neg( h ) )