--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/app/src/main/java/ch/ethz/ssh2/crypto/cipher/CBCMode.java	Thu Dec 03 11:23:55 2015 -0800
@@ -0,0 +1,71 @@
+/*
+ * Copyright (c) 2006-2011 Christian Plattner. All rights reserved.
+ * Please refer to the LICENSE.txt for licensing details.
+ */
+package ch.ethz.ssh2.crypto.cipher;
+
+/**
+ * CBCMode.
+ *
+ * @author Christian Plattner
+ * @version 2.50, 03/15/10
+ */
+public class CBCMode implements BlockCipher {
+    BlockCipher tc;
+    int blockSize;
+    boolean doEncrypt;
+
+    byte[] cbc_vector;
+    byte[] tmp_vector;
+
+    public void init(boolean forEncryption, byte[] key) {
+    }
+
+    public CBCMode(BlockCipher tc, byte[] iv, boolean doEncrypt)
+    throws IllegalArgumentException {
+        this.tc = tc;
+        this.blockSize = tc.getBlockSize();
+        this.doEncrypt = doEncrypt;
+
+        if (this.blockSize != iv.length)
+            throw new IllegalArgumentException("IV must be " + blockSize
+                                               + " bytes long! (currently " + iv.length + ")");
+
+        this.cbc_vector = new byte[blockSize];
+        this.tmp_vector = new byte[blockSize];
+        System.arraycopy(iv, 0, cbc_vector, 0, blockSize);
+    }
+
+    public int getBlockSize() {
+        return blockSize;
+    }
+
+    private void encryptBlock(byte[] src, int srcoff, byte[] dst, int dstoff) {
+        for (int i = 0; i < blockSize; i++)
+            cbc_vector[i] ^= src[srcoff + i];
+
+        tc.transformBlock(cbc_vector, 0, dst, dstoff);
+        System.arraycopy(dst, dstoff, cbc_vector, 0, blockSize);
+    }
+
+    private void decryptBlock(byte[] src, int srcoff, byte[] dst, int dstoff) {
+        /* Assume the worst, src and dst are overlapping... */
+        System.arraycopy(src, srcoff, tmp_vector, 0, blockSize);
+        tc.transformBlock(src, srcoff, dst, dstoff);
+
+        for (int i = 0; i < blockSize; i++)
+            dst[dstoff + i] ^= cbc_vector[i];
+
+        /* ...that is why we need a tmp buffer. */
+        byte[] swap = cbc_vector;
+        cbc_vector = tmp_vector;
+        tmp_vector = swap;
+    }
+
+    public void transformBlock(byte[] src, int srcoff, byte[] dst, int dstoff) {
+        if (doEncrypt)
+            encryptBlock(src, srcoff, dst, dstoff);
+        else
+            decryptBlock(src, srcoff, dst, dstoff);
+    }
+}