Added Diffie Hellman, X25519, ECDH over Curve25519

app/build.gradle

@@ -19,7 +19,7 @@ plugins {
 ext {
     artifactId = "lazysodium-android"
     groupId = "com.goterl.lazycode"
-    version = '3.2.0'
+    version = '3.3.0'
     description = "Lazysodium (Android) makes it effortless for Android " +
             "developers to get started with Libsodium's cryptography."
     androidTestDir = "src/androidTest/java/com/goterl/lazycode/lazysodium"

app/src/androidTest/java/com/goterl/lazycode/lazysodium/DiffieHellmanAndroidTest.java

@@ -0,0 +1,68 @@
+/*
+ * Copyright (c) Terl Tech Ltd • 31/07/18 18:54 • goterl.com
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v2.0. If a copy of the MPL was not distributed with this
+ * file, you can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+/*
+ * This Java source file was generated by the Gradle 'init' task.
+ */
+import com.goterl.lazycode.lazysodium.exceptions.SodiumException;
+import com.goterl.lazycode.lazysodium.interfaces.Box;
+import com.goterl.lazycode.lazysodium.interfaces.DiffieHellman;
+import com.goterl.lazycode.lazysodium.interfaces.SecretBox;
+import com.goterl.lazycode.lazysodium.interfaces.StreamJava;
+import com.goterl.lazycode.lazysodium.utils.Key;
+import junit.framework.TestCase;
+import org.junit.Test;
+
+public class DiffieHellmanAndroidTest extends BaseTest {
+
+    private String clientSecretKey = "CLIENT_TOP_SECRET_KEY_1234567890";
+    private String serverSecretKey = "SERVER_TOP_SECRET_KEY_1234567890";
+
+
+    @Test
+    public void create() throws SodiumException {
+        DiffieHellman.Lazy dh = (DiffieHellman.Lazy) lazySodium;
+        SecretBox.Lazy box = (SecretBox.Lazy) lazySodium;
+
+        Key secretKeyC = Key.fromPlainString(clientSecretKey);
+        Key publicKeyC = dh.cryptoScalarMultBase(secretKeyC);
+
+        Key secretKeyS = Key.fromPlainString(serverSecretKey);
+        Key publicKeyS = dh.cryptoScalarMultBase(secretKeyS);
+
+        // -----
+        // ON THE CLIENT
+        // -----
+
+        // Compute a shared key for sending from client
+        // to server.
+        Key sharedKey = dh.cryptoScalarMult(secretKeyC, publicKeyS);
+
+        String message = "Hello";
+        byte[] nonce = new byte[Box.NONCEBYTES];
+        String encrypted = box.cryptoSecretBoxEasy(message, nonce, sharedKey);
+
+        // Send 'encrypted' to server...
+
+
+        // -----
+        // ON THE SERVER
+        // -----
+
+        // Compute the shared key for receiving server messages from client
+        Key sharedKeyServer = dh.cryptoScalarMult(secretKeyS, publicKeyC);
+        String decrypted = box.cryptoSecretBoxOpenEasy(encrypted, nonce, sharedKeyServer);
+
+        // 'decrypted' == Hello
+
+        TestCase.assertEquals(message, decrypted);
+    }
+
+
+
+}