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
	exp = mpnew(0);
36
	g = mpnew(0);
37
	r = mpnew(0);
38
	mpsub(pub->p, mpone, exp);
39
	mpdiv(exp, pub->q, exp, r);
40
	if(mpcmp(r, mpzero) != 0)
41
		sysfatal("dsagen foul up");
42
	while(1){
43
		mprand(bits, genrandom, g);
44
		mpmod(g, pub->p, g);
45
		mpexp(g, exp, pub->p, pub->alpha);
46
		if(mpcmp(pub->alpha, mpone) != 0)
47
			break;
48
	}
49
	mpfree(g);
50
	mpfree(exp);
51
 
52
	// create the secret key
53
	mprand(bits, genrandom, priv->secret);
54
	mpmod(priv->secret, pub->p, priv->secret);
55
	mpexp(pub->alpha, priv->secret, pub->p, pub->key);
56
 
57
	return priv;
58
}