PRNG based Symmetric Stream Cipher

An algorithm of symmetric stream cipher is proposed embedding a PRNG within it. Stream ciphers require a random key stream. A simple exclusive OR operation is needed between the randomly generated key stream and the text character to obtain the cipher text. Randomness of the cipher text depends on the randomness of the key stream. A comparative study on randomness of three key streams namely RC4, PM and BBS is observed in this paper. In the study, 13424 key-bits are generated in each key sequence. For each algorithm 300 such key sequences are generated using different keys. The randomness characteristics of 300 key sequences of each algorithm are tested using four basic statistical tests. Results are compared and it is observed that using a PRNG in the proposed algorithm makes it statistically secured.