diff options
Diffstat (limited to 'cipher/elgamal.c')
| -rw-r--r-- | cipher/elgamal.c | 28 |
1 files changed, 20 insertions, 8 deletions
diff --git a/cipher/elgamal.c b/cipher/elgamal.c index 5e6bd0c84..13b8579fe 100644 --- a/cipher/elgamal.c +++ b/cipher/elgamal.c @@ -311,25 +311,37 @@ elg_verify(MPI a, MPI b, MPI input, ELG_public_key *pkey ) int rc; MPI t1; MPI t2; + MPI base[4]; + MPI exp[4]; if( !(mpi_cmp_ui( a, 0 ) > 0 && mpi_cmp( a, pkey->p ) < 0) ) return 0; /* assertion 0 < a < p failed */ t1 = mpi_alloc( mpi_get_nlimbs(a) ); t2 = mpi_alloc( mpi_get_nlimbs(a) ); - /* t1 = (y^a mod p) * (a^b mod p) mod p - * fixme: should be calculated by a call which evalutes - * t1 = y^a * a^b mod p - * direct. - */ - mpi_powm( t1, pkey->y, a, pkey->p ); - mpi_powm( t2, a, b, pkey->p ); - mpi_mulm( t1, t1, t2, pkey->p ); + + #if 0 + /* t1 = (y^a mod p) * (a^b mod p) mod p */ + base[0] = pkey->y; exp[0] = a; + base[1] = a; exp[1] = b; + base[2] = NULL; exp[2] = NULL; + mpi_mulpowm( t1, base, exp, pkey->p ); /* t2 = g ^ input mod p */ mpi_powm( t2, pkey->g, input, pkey->p ); rc = !mpi_cmp( t1, t2 ); + #else + /* t1 = g ^ - input * y ^ a * a ^ b mod p */ + mpi_invm(t2, pkey->g, pkey->p ); + base[0] = t2 ; exp[0] = input; + base[1] = pkey->y; exp[1] = a; + base[2] = a; exp[2] = b; + base[3] = NULL; exp[3] = NULL; + mpi_mulpowm( t1, base, exp, pkey->p ); + rc = !mpi_cmp_ui( t1, 1 ); + + #endif mpi_free(t1); mpi_free(t2); |