CFB

CFB (ciphertext feedback) is often used as a more simplistic alternative to the CBC block cipher mode. It is very useful when an algorithm calls for plaintext values to be encrypted and transferred one at a time. Similar to cipher block chaining, ciphertext feedback uses an IV (initialization vector). It also enables a block cipher to serve as a functional component of a random number generator. In CFB, the previous ciphertext block is encrypted and the output is combined with the current plaintext to establish the current ciphertext block. The entropy that results from CFB is often used in a stream cipher. In truth, the ciphertext feedback mode is primarily intended to derive the base characteristics of a stream cipher directly from a block cipher. Just like the CBC, modifying the IV to the same plaintext block will result in a different output. While the IV isn’t required to be secret, some algorithms view this is a more reliable approach.