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better prime number generator. improved ELG key generation

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This commit is contained in:
Werner Koch 1997-12-19 11:41:47 +00:00
parent 15426c6d96
commit ee8d92fefa
22 changed files with 1225 additions and 623 deletions
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22
cipher/elgamal.c
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@ -94,7 +94,7 @@ gen_k( MPI p )
for(;;) {
if( DBG_CIPHER )
fputc('.', stderr);
mpi_set_bytes( k, nbits, get_random_byte, 1 );
mpi_set_bytes( k, nbits , get_random_byte, 1 );
if( !(mpi_cmp( k, p_1 ) < 0) ) /* check: k < (p-1) */
continue; /* no */
if( !(mpi_cmp_ui( k, 0 ) > 0) ) /* check: k > 0 */
@ -123,19 +123,23 @@ elg_generate( ELG_public_key *pk, ELG_secret_key *sk, unsigned nbits )
MPI x; /* the secret exponent */
MPI y;
MPI temp;
unsigned qbits;
p = NULL;
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 );
/*do {*/
mpi_free(p);
/* FIXME!!!! Should generate a strong prime */
p = generate_public_prime( nbits );
mpi_sub_ui(p_min1, p, 1);
/*} while if( mpi_gcd( temp, k, p_1 ) )*/
if( nbits < 512 )
qbits = 120;
else if( nbits <= 1024 )
qbits = 160;
else if( nbits <= 2048 )
qbits = 200;
else
qbits = 240;
g = mpi_alloc(1);
p = generate_elg_prime( nbits, qbits, g );
mpi_sub_ui(p_min1, p, 1);
g = mpi_alloc_set_ui(3); /* fixme: 3 is bad (but better than 2)*/
/* select a random number which has these properties:
* 0 < x < p-1
*/