1 files changed, 29 insertions, 0 deletions
diff --git a/src/libsec/port/egverify.c b/src/libsec/port/egverify.c
new file mode 100644
index 00000000..29a95156
--- /dev/null
+++ b/src/libsec/port/egverify.c
@@ -0,0 +1,29 @@
+#include "os.h"
+#include <mp.h>
+#include <libsec.h>
+
+int
+egverify(EGpub *pub, EGsig *sig, mpint *m)
+{
+	mpint *p = pub->p, *alpha = pub->alpha;
+	mpint *r = sig->r, *s = sig->s;
+	mpint *v1, *v2, *rs;
+	int rv = -1;
+
+	if(mpcmp(r, mpone) < 0 || mpcmp(r, p) >= 0)
+		return rv;
+	v1 = mpnew(0);
+	rs = mpnew(0);
+	v2 = mpnew(0);
+	mpexp(pub->key, r, p, v1);
+	mpexp(r, s, p, rs);
+	mpmul(v1, rs, v1);
+	mpmod(v1, p, v1);
+	mpexp(alpha, m, p, v2);
+	if(mpcmp(v1, v2) == 0)
+		rv = 0;
+	mpfree(v1);
+	mpfree(rs);
+	mpfree(v2);
+	return rv;
+}