security-and-privacy/gnupg
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The plumbing necessary to create DSA keys with variable sized q.

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Not yet used (q==160).
This commit is contained in:
David Shaw 2006-04-20 18:40:37 +00:00
parent 99b1f3e1da
commit 2f94329422
4 changed files with 34 additions and 9 deletions
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32
cipher/dsa.c
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@ -1,5 +1,5 @@
/* dsa.c - DSA signature algorithm
* Copyright (C) 1998, 1999, 2000 Free Software Foundation, Inc.
* Copyright (C) 1998, 1999, 2000, 2003, 2006 Free Software Foundation, Inc.
*
* This file is part of GnuPG.
*
@ -49,7 +49,8 @@ typedef struct {
static MPI gen_k( MPI q );
static void test_keys( DSA_secret_key *sk, unsigned qbits );
static int check_secret_key( DSA_secret_key *sk );
static void generate( DSA_secret_key *sk, unsigned nbits, MPI **ret_factors );
static void generate( DSA_secret_key *sk, unsigned nbits, unsigned qbits,
MPI **ret_factors );
static void sign(MPI r, MPI s, MPI input, DSA_secret_key *skey);
static int verify(MPI r, MPI s, MPI input, DSA_public_key *pkey);
@ -168,20 +169,20 @@ test_keys( DSA_secret_key *sk, unsigned qbits )
* and an array with the n-1 factors of (p-1)
*/
static void
generate( DSA_secret_key *sk, unsigned nbits, MPI **ret_factors )
generate( DSA_secret_key *sk, unsigned nbits, unsigned qbits,
MPI **ret_factors )
{
MPI p; /* the prime */
MPI q; /* the 160 bit prime factor */
MPI q; /* the prime factor */
MPI g; /* the generator */
MPI y; /* g^x mod p */
MPI x; /* the secret exponent */
MPI h, e; /* helper */
unsigned qbits;
byte *rndbuf;
assert( nbits >= 512 && nbits <= 1024 );
assert( qbits >= 160 );
qbits = 160;
p = generate_elg_prime( 1, nbits, qbits, NULL, ret_factors );
/* get q out of factors */
q = mpi_copy((*ret_factors)[0]);
@ -207,7 +208,6 @@ generate( DSA_secret_key *sk, unsigned nbits, MPI **ret_factors )
* is the secret part. */
if( DBG_CIPHER )
log_debug("choosing a random x ");
assert( qbits >= 160 );
x = mpi_alloc_secure( mpi_get_nlimbs(q) );
mpi_sub_ui( h, q, 1 ); /* put q-1 into h */
rndbuf = NULL;
@ -364,15 +364,22 @@ verify(MPI r, MPI s, MPI hash, DSA_public_key *pkey )
************** interface ******************
*********************************************/
/* DSA2 has a variable-sized q, which adds an extra parameter to the
pubkey generation. I'm doing this as a different function as it is
only called from one place and is thus cleaner than revamping the
pubkey_generate interface to carry an extra parameter which would
be meaningless for all algorithms other than DSA. */
int
dsa_generate( int algo, unsigned nbits, MPI *skey, MPI **retfactors )
dsa2_generate( int algo, unsigned nbits, unsigned qbits,
MPI *skey, MPI **retfactors )
{
DSA_secret_key sk;
if( algo != PUBKEY_ALGO_DSA )
return G10ERR_PUBKEY_ALGO;
generate( &sk, nbits, retfactors );
generate( &sk, nbits, qbits, retfactors );
skey[0] = sk.p;
skey[1] = sk.q;
skey[2] = sk.g;
@ -382,6 +389,13 @@ dsa_generate( int algo, unsigned nbits, MPI *skey, MPI **retfactors )
}
int
dsa_generate( int algo, unsigned nbits, MPI *skey, MPI **retfactors )
{
return dsa2_generate(algo,nbits,160,skey,retfactors);
}
int
dsa_check_secret_key( int algo, MPI *skey )
{