Replaced insecure Minecraft account authentication with server join technique

src/main/java/eu/crushedpixel/replaymod/online/authentication/AuthenticationHash.java

@@ -0,0 +1,44 @@
+package eu.crushedpixel.replaymod.online.authentication;
+
+import net.minecraft.client.Minecraft;
+
+import java.util.Random;
+
+public class AuthenticationHash {
+
+    private static final Random random = new Random();
+
+    public AuthenticationHash() {
+        username = Minecraft.getMinecraft().getSession().getUsername();
+        currentTime = System.currentTimeMillis();
+        randomLong = random.nextLong();
+        hash = getAuthenticationHash();
+    }
+
+    public final String username;
+    public final long currentTime;
+    public final long randomLong;
+    public final String hash;
+
+    private String getAuthenticationHash() {
+        StringBuilder builder = new StringBuilder();
+        builder.append(username);
+        builder.append(currentTime);
+        builder.append(randomLong);
+
+        String md5 = builder.toString();
+
+        try {
+            java.security.MessageDigest md = java.security.MessageDigest.getInstance("MD5");
+            byte[] array = md.digest(md5.getBytes());
+            StringBuffer sb = new StringBuffer();
+            for (int i = 0; i < array.length; ++i) {
+                sb.append(Integer.toHexString((array[i] & 0xFF) | 0x100).substring(1,3));
+            }
+            return sb.toString();
+        } catch (java.security.NoSuchAlgorithmException e) {
+            e.printStackTrace();
+        }
+        return null;
+    }
+}