Stream Cipher

Stream Cipher processes messages (plaintext) a bit or byte as a stream at a time when encrypting or decrypting. It typically has a pseudorandom keystream which can be used to destroy statistically properties in message, as shown in the following formulae:

$$ -C_i = m_i \oplus \text{ streamkey}_i $$

Where:

$C$ is the ciphertext
$m$ is the message in plaintext

However, the keystream should be of one use# to prevent the possible recovery of the plaintext. Therefore, Stream Cipher exhibits the properties where it will encrypt the data with long period with no repetitions and statistically random. Though it does rely on large key size and have a large linear complexity.

Examples of Stream Cipher are:

RC4#
SEAL
HC-256

Links to this page

TNS3131 Chapter 2: Conventional Encryption and Message Confidentiality

Stream Cipher
Rotor Machine

Rotor Machine is an electro-mechanical stream cipher# device that could perform #Substitution Cryptography with a more complex scheme.
RC4

RC4 is a simple and fast, byte-oriented #Stream Cipher, designed by Ron Rivest and owned by RSA DSI, which accepts variable key size. It is widely adopted such as in #SSL/TSL and Wireless WEP. The key forms random permutation of all 8-bit values and use that to collect input information processed a byte at a time. It has been proved to be insecure and easily breakable recently.
Cryptography

Stream Cipher#