diff options
Diffstat (limited to '')
| -rw-r--r-- | cipher/primegen.c | 53 |
1 files changed, 41 insertions, 12 deletions
diff --git a/cipher/primegen.c b/cipher/primegen.c index 6ebaffe6a..26d21acb9 100644 --- a/cipher/primegen.c +++ b/cipher/primegen.c @@ -63,37 +63,49 @@ generate_public_prime( unsigned nbits ) * security from it - The prime number is public and we could also * offer the factors for those who are willing to check that it is * indeed a strong prime. + * + * mode 0: Standard + * 1: Make sure that at least one factor is of size qbits. */ MPI -generate_elg_prime( unsigned pbits, unsigned qbits, MPI g, MPI **ret_factors ) +generate_elg_prime( int mode, unsigned pbits, unsigned qbits, + MPI g, MPI **ret_factors ) { int n; /* number of factors */ int m; /* number of primes in pool */ unsigned fbits; /* length of prime factors */ MPI *factors; /* current factors */ MPI *pool; /* pool of primes */ - MPI q; /* first prime factor */ + MPI q; /* first prime factor (variable)*/ MPI prime; /* prime test value */ + MPI q_factor; /* used for mode 1 */ byte *perms = NULL; int i, j; int count1, count2; unsigned nprime; + unsigned req_qbits = qbits; /* the requested q bits size */ /* find number of needed prime factors */ for(n=1; (pbits - qbits - 1) / n >= qbits; n++ ) ; n--; - if( !n ) + if( !n || (mode==1 && n < 2) ) log_fatal("can't gen prime with pbits=%u qbits=%u\n", pbits, qbits ); - fbits = (pbits - qbits -1) / n; - while( qbits + n*fbits < pbits ) - qbits++; + if( mode == 1 ) { + n--; + fbits = (pbits - 2*req_qbits -1) / n; + qbits = pbits - req_qbits - n*fbits; + } + else { + fbits = (pbits - req_qbits -1) / n; + qbits = pbits - n*fbits; + } if( DBG_CIPHER ) - log_debug("gen prime: pbits=%u qbits=%u fbits=%u n=%d\n", - pbits, qbits, fbits, n ); - + log_debug("gen prime: pbits=%u qbits=%u fbits=%u/%u n=%d\n", + pbits, req_qbits, qbits, fbits, n ); prime = mpi_alloc( (pbits + BITS_PER_MPI_LIMB - 1) / BITS_PER_MPI_LIMB ); q = gen_prime( qbits, 0, 1 ); + q_factor = mode==1? gen_prime( req_qbits, 0, 1 ) : NULL; /* allocate an array to hold the factors + 2 for later usage */ factors = m_alloc_clear( (n+2) * sizeof *factors ); @@ -139,6 +151,8 @@ generate_elg_prime( unsigned pbits, unsigned qbits, MPI g, MPI **ret_factors ) mpi_set( prime, q ); mpi_mul_ui( prime, prime, 2 ); + if( mode == 1 ) + mpi_mul( prime, prime, q_factor ); for(i=0; i < n; i++ ) mpi_mul( prime, prime, factors[i] ); mpi_add_ui( prime, prime, 1 ); @@ -171,18 +185,30 @@ generate_elg_prime( unsigned pbits, unsigned qbits, MPI g, MPI **ret_factors ) putc('\n', stderr); log_mpidump( "prime : ", prime ); log_mpidump( "factor q: ", q ); + if( mode == 1 ) + log_mpidump( "factor q0: ", q_factor ); for(i=0; i < n; i++ ) log_mpidump( "factor pi: ", factors[i] ); log_debug("bit sizes: prime=%u, q=%u", mpi_get_nbits(prime), mpi_get_nbits(q) ); + if( mode == 1 ) + fprintf(stderr, ", q0=%u", mpi_get_nbits(q_factor) ); for(i=0; i < n; i++ ) fprintf(stderr, ", p%d=%u", i, mpi_get_nbits(factors[i]) ); putc('\n', stderr); } if( ret_factors ) { /* caller wants the factors */ - *ret_factors = m_alloc_clear( (n+1) * sizeof **ret_factors ); - for(i=0; i < n; i++ ) - (*ret_factors)[i] = mpi_copy( factors[i] ); + *ret_factors = m_alloc_clear( (n+2) * sizeof **ret_factors); + if( mode == 1 ) { + i = 0; + (*ret_factors)[i++] = mpi_copy( q_factor ); + for(; i <= n; i++ ) + (*ret_factors)[i] = mpi_copy( factors[i] ); + } + else { + for(; i < n; i++ ) + (*ret_factors)[i] = mpi_copy( factors[i] ); + } } if( g ) { /* create a generator (start with 3)*/ @@ -190,6 +216,8 @@ generate_elg_prime( unsigned pbits, unsigned qbits, MPI g, MPI **ret_factors ) MPI b = mpi_alloc( mpi_get_nlimbs(prime) ); MPI pmin1 = mpi_alloc( mpi_get_nlimbs(prime) ); + if( mode == 1 ) + BUG(); /* not yet implemented */ factors[n] = q; factors[n+1] = mpi_alloc_set_ui(2); mpi_sub_ui( pmin1, prime, 1 ); @@ -230,6 +258,7 @@ generate_elg_prime( unsigned pbits, unsigned qbits, MPI g, MPI **ret_factors ) } + static MPI gen_prime( unsigned nbits, int secret, int randomlevel ) { |