diff options
Diffstat (limited to '')
| -rw-r--r-- | cipher/elgamal.c | 24 |
1 files changed, 18 insertions, 6 deletions
diff --git a/cipher/elgamal.c b/cipher/elgamal.c index b211d7f6c..c13181d90 100644 --- a/cipher/elgamal.c +++ b/cipher/elgamal.c @@ -126,6 +126,7 @@ elg_generate( ELG_public_key *pk, ELG_secret_key *sk, MPI y; MPI temp; unsigned qbits; + byte *rndbuf; p_min1 = mpi_alloc( (nbits+BITS_PER_MPI_LIMB-1)/BITS_PER_MPI_LIMB ); temp = mpi_alloc( (nbits+BITS_PER_MPI_LIMB-1)/BITS_PER_MPI_LIMB ); @@ -145,22 +146,33 @@ elg_generate( ELG_public_key *pk, ELG_secret_key *sk, /* select a random number which has these properties: * 0 < x < p-1 * This must be a very good random number because this is the - * secret part. The prime is public and may be shared anyware, - * so a random generator level of 1 has been used for the prime + * secret part. The prime is public and may be shared anyway, + * so a random generator level of 1 is used for the prime. */ x = mpi_alloc_secure( nbits/BITS_PER_MPI_LIMB ); if( DBG_CIPHER ) log_debug("choosing a random x "); + rndbuf = NULL; do { - byte *rndbuf; if( DBG_CIPHER ) fputc('.', stderr); - rndbuf = get_random_bits( nbits, 2, 1 ); + if( rndbuf ) { /* change only some of the higher bits */ + if( nbits < 16 ) {/* should never happen ... */ + m_free(rndbuf); + rndbuf = get_random_bits( nbits, 2, 1 ); + } + else { + char *r = get_random_bits( 16, 2, 1 ); + memcpy(rndbuf, r, 16 ); + m_free(r); + } + } + else + rndbuf = get_random_bits( nbits, 2, 1 ); mpi_set_buffer( x, rndbuf, (nbits+7)/8, 0 ); - m_free(rndbuf); mpi_clear_highbit( x, nbits+1 ); - log_mpidump(" x: ", x ); } while( !( mpi_cmp_ui( x, 0 )>0 && mpi_cmp( x, p_min1 )<0 ) ); + m_free(rndbuf); y = mpi_alloc(nbits/BITS_PER_MPI_LIMB); mpi_powm( y, g, x, p ); |