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 DSAsig*
 6 0fc65b37 2004-03-21 devnull dsasign(DSApriv *priv, mpint *m)
 7 0fc65b37 2004-03-21 devnull {
 8 0fc65b37 2004-03-21 devnull 	DSApub *pub = &priv->pub;
 9 0fc65b37 2004-03-21 devnull 	DSAsig *sig;
10 0fc65b37 2004-03-21 devnull 	mpint *qm1, *k, *kinv, *r, *s;
11 0fc65b37 2004-03-21 devnull 	mpint *q = pub->q, *p = pub->p, *alpha = pub->alpha;
12 0fc65b37 2004-03-21 devnull 	int qlen = mpsignif(q);
13 0fc65b37 2004-03-21 devnull 
14 0fc65b37 2004-03-21 devnull 	qm1 = mpnew(0);
15 0fc65b37 2004-03-21 devnull 	kinv = mpnew(0);
16 0fc65b37 2004-03-21 devnull 	r = mpnew(0);
17 0fc65b37 2004-03-21 devnull 	s = mpnew(0);
18 0fc65b37 2004-03-21 devnull 	k = mpnew(0);
19 0fc65b37 2004-03-21 devnull 	mpsub(pub->q, mpone, qm1);
20 0fc65b37 2004-03-21 devnull 
21 cbeb0b26 2006-04-01 devnull 	/* find a k that has an inverse mod q */
22 0fc65b37 2004-03-21 devnull 	while(1){
23 0fc65b37 2004-03-21 devnull 		mprand(qlen, genrandom, k);
24 0fc65b37 2004-03-21 devnull 		if((mpcmp(mpone, k) > 0) || (mpcmp(k, pub->q) >= 0))
25 0fc65b37 2004-03-21 devnull 			continue;
26 0fc65b37 2004-03-21 devnull 		mpextendedgcd(k, q, r, kinv, s);
27 0fc65b37 2004-03-21 devnull 		if(mpcmp(r, mpone) != 0)
28 0fc65b37 2004-03-21 devnull 			sysfatal("dsasign: pub->q not prime");
29 0fc65b37 2004-03-21 devnull 		break;
30 0fc65b37 2004-03-21 devnull 	}
31 0fc65b37 2004-03-21 devnull 
32 cbeb0b26 2006-04-01 devnull   	/* make kinv positive */
33 0fc65b37 2004-03-21 devnull 	mpmod(kinv, pub->q, kinv);
34 0fc65b37 2004-03-21 devnull 
35 cbeb0b26 2006-04-01 devnull 	/* r = ((alpha**k) mod p) mod q */
36 0fc65b37 2004-03-21 devnull 	mpexp(alpha, k, p, r);
37 0fc65b37 2004-03-21 devnull 	mpmod(r, q, r);
38 0fc65b37 2004-03-21 devnull 
39 cbeb0b26 2006-04-01 devnull 	/* s = (kinv*(m + ar)) mod q */
40 0fc65b37 2004-03-21 devnull 	mpmul(r, priv->secret, s);
41 0fc65b37 2004-03-21 devnull 	mpadd(s, m, s);
42 0fc65b37 2004-03-21 devnull 	mpmul(s, kinv, s);
43 0fc65b37 2004-03-21 devnull 	mpmod(s, q, s);
44 0fc65b37 2004-03-21 devnull 
45 0fc65b37 2004-03-21 devnull 	sig = dsasigalloc();
46 0fc65b37 2004-03-21 devnull 	sig->r = r;
47 0fc65b37 2004-03-21 devnull 	sig->s = s;
48 0fc65b37 2004-03-21 devnull 	mpfree(qm1);
49 0fc65b37 2004-03-21 devnull 	mpfree(k);
50 0fc65b37 2004-03-21 devnull 	mpfree(kinv);
51 0fc65b37 2004-03-21 devnull 	return sig;
52 0fc65b37 2004-03-21 devnull }