diff --git a/fuzz/happy.js b/fuzz/happy.js
new file mode 100644
index 0000000..4b4ad9a
--- /dev/null
+++ b/fuzz/happy.js
@@ -0,0 +1,29 @@
+'use strict';
+
+var assert = require('assert'),
+	crypto = require('crypto');
+
+var keygen = require('./keygen');
+
+var conv = require('../');
+
+var sslalgs = {
+	'ES256': 'RSA-SHA256',
+	'ES384': 'RSA-SHA384',
+	'ES512': 'RSA-SHA512'
+};
+
+['ES256', 'ES384', 'ES512'].forEach(function (alg) {
+	for (var i = 0; i < 10; ++i) {
+		var pem = keygen(alg);
+
+		for (var j = 0; j < 10000; ++j) {
+			var der = crypto
+				.createSign(sslalgs[alg])
+				.update(crypto.randomBytes((Math.random() * (256 - 1) | 0) + 1))
+				.sign(pem);
+
+			assert(conv.joseToDer(conv.derToJose(der, alg), alg).equals(der));
+		}
+	}
+});
diff --git a/fuzz/keygen.js b/fuzz/keygen.js
new file mode 100644
index 0000000..19547fe
--- /dev/null
+++ b/fuzz/keygen.js
@@ -0,0 +1,46 @@
+'use strict';
+
+var base64url = require('base64-url').escape,
+	EC = require('elliptic').ec,
+	jwkToPem = require('jwk-to-pem');
+
+var curves = {
+		ES256: 'p256',
+		ES384: 'p384',
+		ES512: 'p521'
+	},
+	jwkCurves = {
+		ES256: 'P-256',
+		ES384: 'P-384',
+		ES512: 'P-521'
+	};
+
+function b64(val) {
+	val = val.toString('hex', 2);
+	val = new Buffer(val, 'hex');
+	val = val.toString('base64');
+	val = base64url(val);
+	return val;
+}
+
+function keygen(alg) {
+	var curve = new EC(curves[alg]);
+
+	var keypair = curve.genKeyPair();
+	var priv = keypair.getPrivate();
+	var pub = keypair.getPublic();
+
+	var jwk = {
+		kty: 'EC',
+		crv: jwkCurves[alg],
+		x: b64(pub.getX()),
+		y: b64(pub.getY()),
+		d: b64(priv)
+	};
+
+	var pem = jwkToPem(jwk, { private: true });
+
+	return pem;
+}
+
+module.exports = keygen;
diff --git a/package.json b/package.json
index 07f2740..273415a 100644
--- a/package.json
+++ b/package.json
@@ -33,7 +33,9 @@
     "bench": "^0.3.5",
     "chai": "^3.0.0",
     "coveralls": "^2.11.2",
+    "elliptic": "^6.0.1",
     "istanbul": "^0.3.15",
+    "jwk-to-pem": "^1.2.2",
     "mocha": "^2.2.5"
   }
 }