a

libsec/egsign.c

@@ -0,0 +1,43 @@
+#include "os.h"
+#include <mp.h>
+#include <libsec.h>
+
+EGsig*
+egsign(EGpriv *priv, mpint *m)
+{
+	EGpub *pub = &priv->pub;
+	EGsig *sig;
+	mpint *pm1, *k, *kinv, *r, *s;
+	mpint *p = pub->p, *alpha = pub->alpha;
+	int plen = mpsignif(p);
+
+	pm1 = mpnew(0);
+	kinv = mpnew(0);
+	r = mpnew(0);
+	s = mpnew(0);
+	k = mpnew(0);
+	mpsub(p, mpone, pm1);
+	while(1){
+		mprand(plen, genrandom, k);
+		if((mpcmp(mpone, k) > 0) || (mpcmp(k, pm1) >= 0))
+			continue;
+		mpextendedgcd(k, pm1, r, kinv, s);
+		if(mpcmp(r, mpone) != 0)
+			continue;
+		break;
+	}
+	mpmod(kinv, pm1, kinv);  // make kinv positive
+	mpexp(alpha, k, p, r);
+	mpmul(priv->secret, r, s);
+	mpmod(s, pm1, s);
+	mpsub(m, s, s);
+	mpmul(kinv, s, s);
+	mpmod(s, pm1, s);
+	sig = egsigalloc();
+	sig->r = r;
+	sig->s = s;
+	mpfree(pm1);
+	mpfree(k);
+	mpfree(kinv);
+	return sig;
+}