Block ciphers operate on large blocks of digits with a fixed, unvarying transformation. Stream ciphers represent a different approach to symmetric encryption from block ciphers. The seed value serves as the cryptographic key for decrypting the ciphertext stream. The pseudorandom keystream is typically generated serially from a random seed value using digital shift registers.
In practice, a digit is typically a bit and the combining operation is an exclusive-or (XOR). Since encryption of each digit is dependent on the current state of the cipher, it is also known as state cipher. 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. The operation of the keystream generator in A5/1, an LFSR-based stream cipher used to encrypt mobile phone conversations.Ī stream cipher is a symmetric key cipher where plaintext digits are combined with a pseudorandom cipher digit stream ( keystream). JSTOR ( October 2021) ( Learn how and when to remove this template message).Unsourced material may be challenged and removed. Please help improve this article by adding citations to reliable sources. This article needs additional citations for verification.
