1 0fc65b37 2004-03-21 devnull #include "os.h"
 2 0fc65b37 2004-03-21 devnull #include <mp.h>
 3 0fc65b37 2004-03-21 devnull #include <libsec.h>
 4 0fc65b37 2004-03-21 devnull 
 5 0fc65b37 2004-03-21 devnull DSApriv*
 6 0fc65b37 2004-03-21 devnull dsagen(DSApub *opub)
 7 0fc65b37 2004-03-21 devnull {
 8 0fc65b37 2004-03-21 devnull 	DSApub *pub;
 9 0fc65b37 2004-03-21 devnull 	DSApriv *priv;
10 0fc65b37 2004-03-21 devnull 	mpint *exp;
11 0fc65b37 2004-03-21 devnull 	mpint *g;
12 0fc65b37 2004-03-21 devnull 	mpint *r;
13 0fc65b37 2004-03-21 devnull 	int bits;
14 0fc65b37 2004-03-21 devnull 
15 0fc65b37 2004-03-21 devnull 	priv = dsaprivalloc();
16 0fc65b37 2004-03-21 devnull 	pub = &priv->pub;
17 0fc65b37 2004-03-21 devnull 
18 0fc65b37 2004-03-21 devnull 	if(opub != nil){
19 0fc65b37 2004-03-21 devnull 		pub->p = mpcopy(opub->p);
20 0fc65b37 2004-03-21 devnull 		pub->q = mpcopy(opub->q);
21 0fc65b37 2004-03-21 devnull 	} else {
22 0fc65b37 2004-03-21 devnull 		pub->p = mpnew(0);
23 0fc65b37 2004-03-21 devnull 		pub->q = mpnew(0);
24 0fc65b37 2004-03-21 devnull 		DSAprimes(pub->q, pub->p, nil);
25 0fc65b37 2004-03-21 devnull 	}
26 0fc65b37 2004-03-21 devnull 	bits = Dbits*pub->p->top;
27 0fc65b37 2004-03-21 devnull 
28 0fc65b37 2004-03-21 devnull 	pub->alpha = mpnew(0);
29 0fc65b37 2004-03-21 devnull 	pub->key = mpnew(0);
30 0fc65b37 2004-03-21 devnull 	priv->secret = mpnew(0);
31 0fc65b37 2004-03-21 devnull 
32 0fc65b37 2004-03-21 devnull 	// find a generator alpha of the multiplicative
33 0fc65b37 2004-03-21 devnull 	// group Z*p, i.e., of order n = p-1.  We use the
34 0fc65b37 2004-03-21 devnull 	// fact that q divides p-1 to reduce the exponent.
35 0fc65b37 2004-03-21 devnull 	exp = mpnew(0);
36 0fc65b37 2004-03-21 devnull 	g = mpnew(0);
37 0fc65b37 2004-03-21 devnull 	r = mpnew(0);
38 0fc65b37 2004-03-21 devnull 	mpsub(pub->p, mpone, exp);
39 0fc65b37 2004-03-21 devnull 	mpdiv(exp, pub->q, exp, r);
40 0fc65b37 2004-03-21 devnull 	if(mpcmp(r, mpzero) != 0)
41 0fc65b37 2004-03-21 devnull 		sysfatal("dsagen foul up");
42 0fc65b37 2004-03-21 devnull 	while(1){
43 0fc65b37 2004-03-21 devnull 		mprand(bits, genrandom, g);
44 0fc65b37 2004-03-21 devnull 		mpmod(g, pub->p, g);
45 0fc65b37 2004-03-21 devnull 		mpexp(g, exp, pub->p, pub->alpha);
46 0fc65b37 2004-03-21 devnull 		if(mpcmp(pub->alpha, mpone) != 0)
47 0fc65b37 2004-03-21 devnull 			break;
48 0fc65b37 2004-03-21 devnull 	}
49 0fc65b37 2004-03-21 devnull 	mpfree(g);
50 0fc65b37 2004-03-21 devnull 	mpfree(exp);
51 0fc65b37 2004-03-21 devnull 
52 0fc65b37 2004-03-21 devnull 	// create the secret key
53 0fc65b37 2004-03-21 devnull 	mprand(bits, genrandom, priv->secret);
54 0fc65b37 2004-03-21 devnull 	mpmod(priv->secret, pub->p, priv->secret);
55 0fc65b37 2004-03-21 devnull 	mpexp(pub->alpha, priv->secret, pub->p, pub->key);
56 0fc65b37 2004-03-21 devnull 
57 0fc65b37 2004-03-21 devnull 	return priv;
58 0fc65b37 2004-03-21 devnull }