return the underlying block cipher that we are wrapping.
Process one block of input from the array in and write it to the out array.
reset the chaining vector back to the IV and reset the underlying cipher.
Initialize the cipher and, possibly, the initialization vector (IV). If the cipher is already initialized a new IV can be set without the overhead of a new key setup: init(forEncryption, null, newIV)
implements Cipher-Block-Chaining (CBC) mode on top of a simple cipher.