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-rw-r--r--cipher/dsa.c205
1 files changed, 42 insertions, 163 deletions
diff --git a/cipher/dsa.c b/cipher/dsa.c
index 07f9e7075..8024ac0a2 100644
--- a/cipher/dsa.c
+++ b/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_powm( t1, pkey->y, a, pkey->p );
- mpi_powm( t2, a, b, pkey->p );
- mpi_mulm( t1, t1, t2, pkey->p );
-
- mpi_powm( t2, pkey->g, input, pkey->p );
-
- rc = !mpi_cmp( t1, t2 );
-
- mpi_free(t1);
- mpi_free(t2);
+ MPI w, u1, u2, v;
+ MPI base[3];
+ MPI exp[3];
+
+ 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 */
+
+ 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) );
+
+ /* w = s^(-1) mod q */
+ mpi_invm( w, s, pkey->q );
+
+ /* 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;
}
generated by cgit v1.2.3 (git 2.25.1) at 2025-04-29 14:22:29 +0000