--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/ch/ethz/ssh2/crypto/cipher/CTRMode.java	Fri Jul 18 11:21:46 2014 -0700
@@ -0,0 +1,65 @@
+/*
+ * Copyright (c) 2006-2011 Christian Plattner. All rights reserved.
+ * Please refer to the LICENSE.txt for licensing details.
+ */
+package ch.ethz.ssh2.crypto.cipher;
+
+/**
+ * This is CTR mode as described in draft-ietf-secsh-newmodes-XY.txt
+ * 
+ * @author Christian Plattner
+ * @version 2.50, 03/15/10
+ */
+public class CTRMode implements BlockCipher
+{
+	byte[] X;
+	byte[] Xenc;
+
+	BlockCipher bc;
+	int blockSize;
+	boolean doEncrypt;
+
+	int count = 0;
+
+	public void init(boolean forEncryption, byte[] key)
+	{
+	}
+
+	public CTRMode(BlockCipher tc, byte[] iv, boolean doEnc) throws IllegalArgumentException
+	{
+		bc = tc;
+		blockSize = bc.getBlockSize();
+		doEncrypt = doEnc;
+
+		if (blockSize != iv.length)
+			throw new IllegalArgumentException("IV must be " + blockSize + " bytes long! (currently " + iv.length + ")");
+
+		X = new byte[blockSize];
+		Xenc = new byte[blockSize];
+
+		System.arraycopy(iv, 0, X, 0, blockSize);
+	}
+
+	public final int getBlockSize()
+	{
+		return blockSize;
+	}
+
+	public final void transformBlock(byte[] src, int srcoff, byte[] dst, int dstoff)
+	{
+		bc.transformBlock(X, 0, Xenc, 0);
+
+		for (int i = 0; i < blockSize; i++)
+		{
+			dst[dstoff + i] = (byte) (src[srcoff + i] ^ Xenc[i]);
+		}
+
+		for (int i = (blockSize - 1); i >= 0; i--)
+		{
+			X[i]++;
+			if (X[i] != 0)
+				break;
+
+		}
+	}
+}