Some embodiments of a method and apparatus for encrypting and decrypting data have been presented. In one embodiment, a stream cipher is run in parallel with a block cipher to output a stream of bits with a length equal to a number of ciphertext blocks in an output stream of the block cipher. The method may further include pre-processing a current plaintext block based on the stream of bits and the number of ciphertext blocks in the output stream of the block cipher. Then the block cipher may encipher the pre-processed block to generate a current ciphertext block.