/*  * This file is part of the UCB release of Plan 9. It is subject to the license * terms in the LICENSE file found in the top-level directory of this * distribution and at http://akaros.cs.berkeley.edu/files/Plan9License. No * part of the UCB release of Plan 9, including this file, may be copied, * modified, propagated, or distributed except according to the terms contained * in the LICENSE file. */ #include "os.h"#include <mp.h>#include <libsec.h> intdsaverify(DSApub *pub, DSAsig *sig, mpint *m){	int rv = -1;	mpint *u1, *u2, *v, *sinv; 	if(mpcmp(sig->r, mpone) < 0 || mpcmp(sig->r, pub->q) >= 0)		return rv;	if(mpcmp(sig->s, mpone) < 0 || mpcmp(sig->s, pub->q) >= 0)		return rv;	u1 = mpnew(0);	u2 = mpnew(0);	v = mpnew(0);	sinv = mpnew(0); 	// find (s**-1) mod q, make sure it exists	mpextendedgcd(sig->s, pub->q, u1, sinv, v);	if(mpcmp(u1, mpone) != 0)		goto out; 	// u1 = (sinv * m) mod q, u2 = (r * sinv) mod q	mpmul(sinv, m, u1);	mpmod(u1, pub->q, u1);	mpmul(sig->r, sinv, u2);	mpmod(u2, pub->q, u2); 	// v = (((alpha**u1)*(key**u2)) mod p) mod q	mpexp(pub->alpha, u1, pub->p, sinv);	mpexp(pub->key, u2, pub->p, v);	mpmul(sinv, v, v);	mpmod(v, pub->p, v);	mpmod(v, pub->q, v); 	if(mpcmp(v, sig->r) == 0)		rv = 0;out:	mpfree(v);	mpfree(u1);	mpfree(u2);	mpfree(sinv);	return rv;}