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.