--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/app/src/main/java/ch/ethz/ssh2/crypto/digest/MAC.java	Thu Dec 03 11:23:55 2015 -0800
@@ -0,0 +1,116 @@
+/*
+ * Copyright (c) 2006-2011 Christian Plattner. All rights reserved.
+ * Please refer to the LICENSE.txt for licensing details.
+ */
+package ch.ethz.ssh2.crypto.digest;
+
+import java.io.IOException;
+import java.security.DigestException;
+
+/**
+ * MAC.
+ *
+ * @author Christian Plattner
+ * @version 2.50, 03/15/10
+ */
+public final class MAC {
+    private Digest mac;
+    private int size;
+
+    public static String[] getMacList() {
+        // Higher priority (stronger) first. Added SHA-2 algorithms as in RFC 6668
+        return new String[] {
+                             // "hmac-sha2-512",    // fails interop w/ centos6
+                             "hmac-sha2-256",
+                             "hmac-sha1",
+                             "hmac-sha1-96",
+                             "hmac-md5",
+                             "hmac-md5-96"
+                             };
+    }
+
+    public static void checkMacList(final String[] macs) {
+        for (String m : macs) {
+            getKeyLen(m);
+        }
+    }
+
+    public static int getKeyLen(final String type) {
+        if (type.equals("hmac-sha1")) {
+            return 20;
+        }
+
+        if (type.equals("hmac-sha1-96")) {
+            return 20;
+        }
+
+        if (type.equals("hmac-md5")) {
+            return 16;
+        }
+
+        if (type.equals("hmac-md5-96")) {
+            return 16;
+        }
+
+        if (type.equals("hmac-sha2-256")) {
+            return 32;
+        }
+
+        if (type.equals("hmac-sha2-512")) {
+            return 64;
+        }
+
+        throw new IllegalArgumentException(String.format("Unknown algorithm %s", type));
+    }
+
+    public MAC(final String type, final byte[] key) throws DigestException {
+        if (type.equals("hmac-sha1")) {
+            mac = new HMAC(new SHA1(), key, 20);
+        }
+        else if (type.equals("hmac-sha1-96")) {
+            mac = new HMAC(new SHA1(), key, 12);
+        }
+        else if (type.equals("hmac-md5")) {
+            mac = new HMAC(new MD5(), key, 16);
+        }
+        else if (type.equals("hmac-md5-96")) {
+            mac = new HMAC(new MD5(), key, 12);
+        }
+        else if (type.equals("hmac-sha2-256")) {
+            mac = new HMAC(new SHA256(), key, 32);
+        }
+        else if (type.equals("hmac-sha2-512")) {
+            mac = new HMAC(new SHA512(), key, 64);
+        }
+        else {
+            throw new IllegalArgumentException(String.format("Unknown algorithm %s", type));
+        }
+
+        size = mac.getDigestLength();
+    }
+
+    public final void initMac(final int seq) {
+        mac.reset();
+        mac.update((byte)(seq >> 24));
+        mac.update((byte)(seq >> 16));
+        mac.update((byte)(seq >> 8));
+        mac.update((byte)(seq));
+    }
+
+    public final void update(byte[] packetdata, int off, int len) {
+        mac.update(packetdata, off, len);
+    }
+
+    public final void getMac(byte[] out, int off) throws IOException {
+        try {
+            mac.digest(out, off);
+        }
+        catch (DigestException e) {
+            throw new IOException(e);
+        }
+    }
+
+    public final int size() {
+        return size;
+    }
+}