The Cipher Feedback mode is another enhanced mode of ECB which chains together blocks of ciphertext. CFB uses previously generated ciphertext as input to the next encryption to generate pseudorandom outputs which are combined with the plaintext to produce cipher, thereby chaining together the resulting cipher. The CFB is a mode that features the feedback of successive ciphertext segments into the input blocks of the forward cipher to generate output blocks that are exclusive-OR-ed with the plaintext to produce the ciphertext, and vice versa. The CFB mode requires an initialization vector as the initial input block.