The plain text is processed 1-bit at a time & a series of actions is carried out on it for generating one bit of cipher-text.

Correct Answer is : Stream cipher

Explanation:

• A stream cipher is an encryption algorithm that encrypts one bit or byte of plaintext at a time.
• In a stream cipher, each plaintext digit is encrypted one at a time with the corresponding digit of the keystream, to give a digit of the ciphertext stream.
• A stream cipher is a symmetric key cipher. The best way to ensure security with stream ciphers is to use keys just once. And each key should be unrelated to any other you’ve used.