Add encoding test vectors from the spec.

ristretto255_test.go

@@ -78,7 +78,7 @@ var (
 	}}
 )
 
-func TestRistrettoEncoding(t *testing.T) {
+func TestRistrettoBasepointRoundTrip(t *testing.T) {
 	decodedBasepoint := &Element{}
 	err := decodedBasepoint.Decode(compressedRistrettoBasepoint)
 	if err != nil {
@@ -100,6 +100,53 @@ func TestRistrettoEncoding(t *testing.T) {
 	}
 }
 
-func TestRistrettoRoundtrip(t *testing.T) {
+func TestRistrettoRandomRoundtrip(t *testing.T) {
 	// TODO quickcheck
 }
+
+func TestRistrettoSmallMultiplesTestVectors(t *testing.T) {
+	var testVectors = [16]string{
+		// This is the identity point
+		"0000000000000000000000000000000000000000000000000000000000000000",
+		// This is the basepoint
+		"e2f2ae0a6abc4e71a884a961c500515f58e30b6aa582dd8db6a65945e08d2d76",
+		// These are small multiples of the basepoint
+		"6a493210f7499cd17fecb510ae0cea23a110e8d5b901f8acadd3095c73a3b919",
+		"94741f5d5d52755ece4f23f044ee27d5d1ea1e2bd196b462166b16152a9d0259",
+		"da80862773358b466ffadfe0b3293ab3d9fd53c5ea6c955358f568322daf6a57",
+		"e882b131016b52c1d3337080187cf768423efccbb517bb495ab812c4160ff44e",
+		"f64746d3c92b13050ed8d80236a7f0007c3b3f962f5ba793d19a601ebb1df403",
+		"44f53520926ec81fbd5a387845beb7df85a96a24ece18738bdcfa6a7822a176d",
+		"903293d8f2287ebe10e2374dc1a53e0bc887e592699f02d077d5263cdd55601c",
+		"02622ace8f7303a31cafc63f8fc48fdc16e1c8c8d234b2f0d6685282a9076031",
+		"20706fd788b2720a1ed2a5dad4952b01f413bcf0e7564de8cdc816689e2db95f",
+		"bce83f8ba5dd2fa572864c24ba1810f9522bc6004afe95877ac73241cafdab42",
+		"e4549ee16b9aa03099ca208c67adafcafa4c3f3e4e5303de6026e3ca8ff84460",
+		"aa52e000df2e16f55fb1032fc33bc42742dad6bd5a8fc0be0167436c5948501f",
+		"46376b80f409b29dc2b5f6f0c52591990896e5716f41477cd30085ab7f10301e",
+		"e0c418f7c8d9c4cdd7395b93ea124f3ad99021bb681dfc3302a9d99a2e53e64e",
+	}
+
+	// TODO need to use Ristretto addition to do this test properly, see
+	// https://ristretto.group/test_vectors/ristretto255.html
+
+	for i := 0; i < 16; i++ {
+		encoding, err := hex.DecodeString(testVectors[i])
+		if err != nil {
+			t.Error("Bad hex encoding in test vector")
+		}
+		// Decode the test vector to a ristretto255 element
+		decodedPoint := &Element{}
+		err = decodedPoint.Decode(encoding)
+		if err != nil {
+			t.Error("Could not decode test vector")
+		}
+		// Re-encode and check round trips
+		roundtripPoint := decodedPoint.Encode()
+		if !bytes.Equal(encoding, roundtripPoint) {
+			t.Errorf("decode<>encode roundtrip failed on test vector %d", i)
+		}
+		// Check that the test vector encodes i * B
+		// TODO add this (need addition, see above)
+	}
+}