x25519: add RFC7748 Diffie-Hellman Curve25519 tests (#721)

Author: shampoofactory

x25519-dalek/tests/x25519_tests.rs

@@ -115,6 +115,67 @@ fn rfc7748_ladder_test1_vectorset2() {
     do_rfc7748_ladder_test1(input_scalar, input_point, expected);
 }
 
+mod rfc7748_diffie_hellman {
+    use curve25519_dalek::constants::X25519_BASEPOINT;
+    use x25519_dalek::x25519;
+
+    const ALICE_PRIVATE_KEY: [u8; 32] = [
+        0x77, 0x07, 0x6d, 0x0a, 0x73, 0x18, 0xa5, 0x7d, 0x3c, 0x16, 0xc1, 0x72, 0x51, 0xb2, 0x66,
+        0x45, 0xdf, 0x4c, 0x2f, 0x87, 0xeb, 0xc0, 0x99, 0x2a, 0xb1, 0x77, 0xfb, 0xa5, 0x1d, 0xb9,
+        0x2c, 0x2a,
+    ];
+    const ALICE_PUBLIC_KEY: [u8; 32] = [
+        0x85, 0x20, 0xf0, 0x09, 0x89, 0x30, 0xa7, 0x54, 0x74, 0x8b, 0x7d, 0xdc, 0xb4, 0x3e, 0xf7,
+        0x5a, 0x0d, 0xbf, 0x3a, 0x0d, 0x26, 0x38, 0x1a, 0xf4, 0xeb, 0xa4, 0xa9, 0x8e, 0xaa, 0x9b,
+        0x4e, 0x6a,
+    ];
+    const BOB_PRIVATE_KEY: [u8; 32] = [
+        0x5d, 0xab, 0x08, 0x7e, 0x62, 0x4a, 0x8a, 0x4b, 0x79, 0xe1, 0x7f, 0x8b, 0x83, 0x80, 0x0e,
+        0xe6, 0x6f, 0x3b, 0xb1, 0x29, 0x26, 0x18, 0xb6, 0xfd, 0x1c, 0x2f, 0x8b, 0x27, 0xff, 0x88,
+        0xe0, 0xeb,
+    ];
+    const BOB_PUBLIC_KEY: [u8; 32] = [
+        0xde, 0x9e, 0xdb, 0x7d, 0x7b, 0x7d, 0xc1, 0xb4, 0xd3, 0x5b, 0x61, 0xc2, 0xec, 0xe4, 0x35,
+        0x37, 0x3f, 0x83, 0x43, 0xc8, 0x5b, 0x78, 0x67, 0x4d, 0xad, 0xfc, 0x7e, 0x14, 0x6f, 0x88,
+        0x2b, 0x4f,
+    ];
+    const SHARED_SECRET: [u8; 32] = [
+        0x4a, 0x5d, 0x9d, 0x5b, 0xa4, 0xce, 0x2d, 0xe1, 0x72, 0x8e, 0x3b, 0xf4, 0x80, 0x35, 0x0f,
+        0x25, 0xe0, 0x7e, 0x21, 0xc9, 0x47, 0xd1, 0x9e, 0x33, 0x76, 0xf0, 0x9b, 0x3c, 0x1e, 0x16,
+        0x17, 0x42,
+    ];
+
+    fn do_public_from_private_test(private_key: [u8; 32], expected: [u8; 32]) {
+        let public_key = x25519(private_key, X25519_BASEPOINT.0);
+        assert_eq!(public_key, expected);
+    }
+
+    fn do_shared_secret(private_key: [u8; 32], public_key: [u8; 32], expected: [u8; 32]) {
+        let shared_secret = x25519(private_key, public_key);
+        assert_eq!(shared_secret, expected);
+    }
+
+    #[test]
+    fn alice_public_from_private_key() {
+        do_public_from_private_test(ALICE_PRIVATE_KEY, ALICE_PUBLIC_KEY);
+    }
+
+    #[test]
+    fn bob_public_from_private_key() {
+        do_public_from_private_test(BOB_PRIVATE_KEY, BOB_PUBLIC_KEY);
+    }
+
+    #[test]
+    fn alice_public_bob_private_shared_secret() {
+        do_shared_secret(BOB_PRIVATE_KEY, ALICE_PUBLIC_KEY, SHARED_SECRET);
+    }
+
+    #[test]
+    fn alice_private_bob_public_shared_secret() {
+        do_shared_secret(ALICE_PRIVATE_KEY, BOB_PUBLIC_KEY, SHARED_SECRET);
+    }
+}
+
 #[test]
 #[ignore] // Run only if you want to burn a lot of CPU doing 1,000,000 DH operations
 fn rfc7748_ladder_test2() {