Subversion Repositories planix.SVN

Rev

Rev 2 | Details | Compare with Previous | Last modification | View Log | RSS feed

Rev Author Line No. Line
2 - 1 
#include "os.h"
2 
#include <mp.h>
3 
#include <libsec.h>
4 
 
5 
DSApriv*
6 
dsagen(DSApub *opub)
7 
{
8 
	DSApub *pub;
9 
	DSApriv *priv;
10 
	mpint *exp;
11 
	mpint *g;
12 
	mpint *r;
13 
	int bits;
14 
 
15 
	priv = dsaprivalloc();
16 
	pub = &priv->pub;
17 
 
18 
	if(opub != nil){
19 
		pub->p = mpcopy(opub->p);
20 
		pub->q = mpcopy(opub->q);
21 
	} else {
22 
		pub->p = mpnew(0);
23 
		pub->q = mpnew(0);
24 
		DSAprimes(pub->q, pub->p, nil);
25 
	}
26 
	bits = Dbits*pub->p->top;
27 
 
28 
	pub->alpha = mpnew(0);
29 
	pub->key = mpnew(0);
30 
	priv->secret = mpnew(0);
31 
 
32 
	// find a generator alpha of the multiplicative
33 
	// group Z*p, i.e., of order n = p-1.  We use the
34 
	// fact that q divides p-1 to reduce the exponent.
35 
	//
36 
	// This isn't very efficient.  If anyone has a better
37 
	// idea, mail presotto@closedmind.org
38 
	exp = mpnew(0);
39 
	g = mpnew(0);
40 
	r = mpnew(0);
41 
	mpsub(pub->p, mpone, exp);
42 
	mpdiv(exp, pub->q, exp, r);
43 
	if(mpcmp(r, mpzero) != 0)
44 
		sysfatal("dsagen foul up");
45 
	while(1){
46 
		mprand(bits, genrandom, g);
47 
		mpmod(g, pub->p, g);
48 
		mpexp(g, exp, pub->p, pub->alpha);
49 
		if(mpcmp(pub->alpha, mpone) != 0)
50 
			break;
51 
	}
52 
	mpfree(g);
53 
	mpfree(exp);
54 
 
55 
	// create the secret key
56 
	mprand(bits, genrandom, priv->secret);
57 
	mpmod(priv->secret, pub->p, priv->secret);
58 
	mpexp(pub->alpha, priv->secret, pub->p, pub->key);
59 
 
60 
	return priv;
61 
}