Abstract: This paper presents a new methodology for image encryption. The SCAN-CA based image security system belongs to the stream cipher. Its encryption is based on permutations of image pixels and replacement of pixel values. The permutation is done with SCAN pattern generated by the SCAN methodology. SCAN patterns are developed based on the encryption specific SCAN language, which has production rule to generate a different SCAN grammar. The SCAN grammar produces a variable length scan key which is used for image encryption with CA substitution. Image pixel values are replaced using the recursive Cellular Automata substitution. Cellular Automata are dynamical systems in which time and space are discrete. The proposed image encryption method is lossless and it uses a very large number of secret keys. The pixel value permutation is key dependent. Thus, this encryption system finds a great scope in the field of security in terms of, grammar based key generation, large key space with time and space.

Keywords: Image security, Stream Cipher, SCAN methodology, Encryption and Decryption, Cellular Automata