mirror of
git://git.gnupg.org/gnupg.git
synced 2025-07-02 22:46:30 +02:00
partial DSA support
This commit is contained in:
Werner Koch
parent
1b1a6d7e77
commit
a6a8f1e706
62 changed files with 2247 additions and 447 deletions
197
cipher/dsa.c
197
cipher/dsa.c
|
|
@ -32,6 +32,7 @@ void
|
|||
dsa_free_public_key( DSA_public_key *pk )
|
||||
{
|
||||
mpi_free( pk->p ); pk->p = NULL;
|
||||
mpi_free( pk->q ); pk->q = NULL;
|
||||
mpi_free( pk->g ); pk->g = NULL;
|
||||
mpi_free( pk->y ); pk->y = NULL;
|
||||
}
|
||||
|
|
@ -40,121 +41,13 @@ void
|
|||
dsa_free_secret_key( DSA_secret_key *sk )
|
||||
{
|
||||
mpi_free( sk->p ); sk->p = NULL;
|
||||
mpi_free( sk->q ); sk->q = NULL;
|
||||
mpi_free( sk->g ); sk->g = NULL;
|
||||
mpi_free( sk->y ); sk->y = NULL;
|
||||
mpi_free( sk->x ); sk->x = NULL;
|
||||
}
|
||||
|
||||
|
||||
static void
|
||||
test_keys( DSA_public_key *pk, DSA_secret_key *sk, unsigned nbits )
|
||||
{
|
||||
MPI test = mpi_alloc( nbits / BITS_PER_MPI_LIMB );
|
||||
MPI out1_a = mpi_alloc( nbits / BITS_PER_MPI_LIMB );
|
||||
MPI out1_b = mpi_alloc( nbits / BITS_PER_MPI_LIMB );
|
||||
MPI out2 = mpi_alloc( nbits / BITS_PER_MPI_LIMB );
|
||||
|
||||
mpi_set_bytes( test, nbits, get_random_byte, 0 );
|
||||
|
||||
dsa_sign( out1_a, out1_b, test, sk );
|
||||
if( !dsa_verify( out1_a, out1_b, test, pk ) )
|
||||
log_fatal("DSA operation: sign, verify failed\n");
|
||||
|
||||
mpi_free( test );
|
||||
mpi_free( out1_a );
|
||||
mpi_free( out1_b );
|
||||
mpi_free( out2 );
|
||||
}
|
||||
|
||||
|
||||
/****************
|
||||
* generate a random secret exponent k from prime p, so
|
||||
* that k is relatively prime to p-1
|
||||
*/
|
||||
static MPI
|
||||
gen_k( MPI p )
|
||||
{
|
||||
MPI k = mpi_alloc_secure( mpi_get_nlimbs(p) );
|
||||
MPI temp = mpi_alloc( mpi_get_nlimbs(p) );
|
||||
MPI p_1 = mpi_copy(p);
|
||||
unsigned nbits = mpi_get_nbits(p);
|
||||
|
||||
if( DBG_CIPHER )
|
||||
log_debug("choosing a random k ");
|
||||
mpi_sub_ui( p_1, p, 1);
|
||||
for(;;) {
|
||||
if( DBG_CIPHER )
|
||||
fputc('.', stderr);
|
||||
mpi_set_bytes( k, nbits, get_random_byte, 1 );
|
||||
mpi_set_highbit( k, nbits-1 ); /* make sure it's high (really needed?) */
|
||||
if( mpi_cmp( k, p_1 ) >= 0 )
|
||||
continue; /* is not smaller than (p-1) */
|
||||
if( mpi_gcd( temp, k, p_1 ) )
|
||||
break; /* okay, k is relatively prime to (p-1) */
|
||||
}
|
||||
if( DBG_CIPHER )
|
||||
fputc('\n', stderr);
|
||||
mpi_free(p_1);
|
||||
mpi_free(temp);
|
||||
|
||||
return k;
|
||||
}
|
||||
|
||||
/****************
|
||||
* Generate a key pair with a key of size NBITS
|
||||
* Returns: 2 structures filles with all needed values
|
||||
*/
|
||||
void
|
||||
dsa_generate( DSA_public_key *pk, DSA_secret_key *sk, unsigned nbits )
|
||||
{
|
||||
MPI p; /* the prime */
|
||||
MPI g;
|
||||
MPI x; /* the secret exponent */
|
||||
MPI y;
|
||||
|
||||
p = generate_public_prime( nbits );
|
||||
/* FIXME: check wether we shall assert that (p-1)/2 is also prime
|
||||
* Schneier votes against it
|
||||
*/
|
||||
g = mpi_alloc_set_ui(3);
|
||||
|
||||
/* select a random number */
|
||||
x = mpi_alloc_secure( nbits/BITS_PER_MPI_LIMB );
|
||||
if( DBG_CIPHER )
|
||||
log_debug("choosing a random x ");
|
||||
do {
|
||||
if( DBG_CIPHER )
|
||||
fputc('.', stderr);
|
||||
mpi_set_bytes( x, nbits, get_random_byte, 1 ); /* fixme: should be 2 */
|
||||
mpi_set_highbit( x, nbits-1 ); /* make sure it's high (needed?) */
|
||||
} while( mpi_cmp( x, p ) >= 0 ); /* x must be smaller than p */
|
||||
|
||||
y = mpi_alloc(nbits/BITS_PER_MPI_LIMB);
|
||||
mpi_powm( y, g, x, p );
|
||||
|
||||
if( DBG_CIPHER ) {
|
||||
fputc('\n', stderr);
|
||||
log_mpidump("dsa p= ", p );
|
||||
log_mpidump("dsa g= ", g );
|
||||
log_mpidump("dsa y= ", y );
|
||||
log_mpidump("dsa x= ", x );
|
||||
}
|
||||
|
||||
|
||||
/* copy the stuff to the key structures */
|
||||
pk->p = mpi_copy(p);
|
||||
pk->g = mpi_copy(g);
|
||||
pk->y = mpi_copy(y);
|
||||
sk->p = p;
|
||||
sk->g = g;
|
||||
sk->y = y;
|
||||
sk->x = x;
|
||||
|
||||
/* now we can test our keys (this should never fail!) */
|
||||
test_keys( pk, sk, nbits - 64 );
|
||||
}
|
||||
|
||||
|
||||
/****************
|
||||
* Test wether the secret key is valid.
|
||||
* Returns: if this is a valid key.
|
||||
|
|
@ -174,72 +67,58 @@ dsa_check_secret_key( DSA_secret_key *sk )
|
|||
|
||||
|
||||
/****************
|
||||
* Make an Elgamal signature out of INPUT
|
||||
* Make a DSA signature out of INPUT
|
||||
*/
|
||||
|
||||
void
|
||||
dsa_sign(MPI a, MPI b, MPI input, DSA_secret_key *skey )
|
||||
dsa_sign(MPI r, MPI s, MPI input, DSA_secret_key *skey )
|
||||
{
|
||||
MPI k;
|
||||
MPI t = mpi_alloc( mpi_get_nlimbs(a) );
|
||||
MPI inv = mpi_alloc( mpi_get_nlimbs(a) );
|
||||
MPI p_1 = mpi_copy(skey->p);
|
||||
|
||||
/*
|
||||
* b = (t * inv) mod (p-1)
|
||||
* b = (t * inv(k,(p-1),(p-1)) mod (p-1)
|
||||
* b = (((M-x*a) mod (p-1)) * inv(k,(p-1),(p-1))) mod (p-1)
|
||||
*
|
||||
*/
|
||||
mpi_sub_ui(p_1, p_1, 1);
|
||||
k = gen_k( skey->p );
|
||||
mpi_powm( a, skey->g, k, skey->p );
|
||||
mpi_mul(t, skey->x, a );
|
||||
mpi_subm(t, input, t, p_1 );
|
||||
while( mpi_is_neg(t) )
|
||||
mpi_add(t, t, p_1);
|
||||
mpi_invm(inv, k, p_1 );
|
||||
mpi_mulm(b, t, inv, p_1 );
|
||||
|
||||
#if 0
|
||||
if( DBG_CIPHER ) {
|
||||
log_mpidump("dsa sign p= ", skey->p);
|
||||
log_mpidump("dsa sign g= ", skey->g);
|
||||
log_mpidump("dsa sign y= ", skey->y);
|
||||
log_mpidump("dsa sign x= ", skey->x);
|
||||
log_mpidump("dsa sign k= ", k);
|
||||
log_mpidump("dsa sign M= ", input);
|
||||
log_mpidump("dsa sign a= ", a);
|
||||
log_mpidump("dsa sign b= ", b);
|
||||
}
|
||||
#endif
|
||||
mpi_free(k);
|
||||
mpi_free(t);
|
||||
mpi_free(inv);
|
||||
mpi_free(p_1);
|
||||
}
|
||||
|
||||
|
||||
/****************
|
||||
* Returns true if the signature composed from A and B is valid.
|
||||
* Returns true if the signature composed from R and S is valid.
|
||||
*/
|
||||
int
|
||||
dsa_verify(MPI a, MPI b, MPI input, DSA_public_key *pkey )
|
||||
dsa_verify(MPI r, MPI s, MPI input, DSA_public_key *pkey )
|
||||
{
|
||||
int rc;
|
||||
MPI t1 = mpi_alloc( mpi_get_nlimbs(a) );
|
||||
MPI t2 = mpi_alloc( mpi_get_nlimbs(a) );
|
||||
MPI w, u1, u2, v;
|
||||
MPI base[3];
|
||||
MPI exp[3];
|
||||
|
||||
mpi_powm( t1, pkey->y, a, pkey->p );
|
||||
mpi_powm( t2, a, b, pkey->p );
|
||||
mpi_mulm( t1, t1, t2, pkey->p );
|
||||
if( !(mpi_cmp_ui( r, 0 ) > 0 && mpi_cmp( r, pkey->q ) < 0) )
|
||||
return 0; /* assertion 0 < r < q failed */
|
||||
if( !(mpi_cmp_ui( s, 0 ) > 0 && mpi_cmp( s, pkey->q ) < 0) )
|
||||
return 0; /* assertion 0 < s < q failed */
|
||||
|
||||
mpi_powm( t2, pkey->g, input, pkey->p );
|
||||
w = mpi_alloc( mpi_get_nlimbs(pkey->q) );
|
||||
u1 = mpi_alloc( mpi_get_nlimbs(pkey->q) );
|
||||
u2 = mpi_alloc( mpi_get_nlimbs(pkey->q) );
|
||||
v = mpi_alloc( mpi_get_nlimbs(pkey->p) );
|
||||
|
||||
rc = !mpi_cmp( t1, t2 );
|
||||
/* w = s^(-1) mod q */
|
||||
mpi_invm( w, s, pkey->q );
|
||||
|
||||
mpi_free(t1);
|
||||
mpi_free(t2);
|
||||
/* u1 = (input * w) mod q */
|
||||
mpi_mulm( u1, input, w, pkey->q );
|
||||
|
||||
/* u2 = r * w mod q */
|
||||
mpi_mulm( u2, r, w, pkey->q );
|
||||
|
||||
/* v = g^u1 * y^u2 mod p mod q */
|
||||
base[0] = pkey->g; exp[0] = u1;
|
||||
base[1] = pkey->y; exp[1] = u2;
|
||||
base[2] = NULL; exp[2] = NULL;
|
||||
mpi_mulpowm( v, base, exp, pkey->p );
|
||||
mpi_fdiv_r( v, v, pkey->q );
|
||||
|
||||
rc = !mpi_cmp( v, r );
|
||||
|
||||
mpi_free(w);
|
||||
mpi_free(u1);
|
||||
mpi_free(u2);
|
||||
mpi_free(v);
|
||||
return rc;
|
||||
}
|
||||
|
||||
|
|
|
|||
Loading…
Add table
Add a link
Reference in a new issue