An encryption method that applies a cryptographic key and algorithm to each binary digit of plain text in order to produce cipher (encrypted) text. This method has become less prevalent in the wake of block cipher techniques.
An algorithm that independent of the plaintext produces a data stream derived from a key, as long as the plaintext which is combined with the plaintext usually with an XOR operation to produce the ciphertext.
A cipher that serially encrypts data, one bit at a time. See also block cipher.