Maximum period word oriented non-binary key sequence generation and its application in image encryption/decryption
K B Sudeepa, K. V. S. V. N. Raju, M S Sannidhan, Abhir Bhandary · 2016
The stream cipher system in which the binary data processed with binary key is known as binary stream cipher system. In this the encryption algorithm is bit by bit XOR operations of plain text bit and corresponding key sequence bit respectively. This concept further generalized to a non binary cipher system defined over any finite field GF (p), where p is prime integer. Again generalizing further it can also be defined a stream cipher system over a ring Z m , arithmetic operations are carried out over modulo m, where m is suitable large composite integers. In our work, non binary word oriented key sequence is generated for the cryptographic application. Since word oriented key sequence is generated, the larger word can be split into smaller word and these can be processed in parallel. The level of randomness properties of generated key sequences is discussed by conducting statistical tests. The effectiveness of the non binary word oriented stream cipher system is based mainly on encryption / decryption algorithm, key generation and its parameters. This paper concentrates on generating non binary word oriented key sequence of maximum period. This generated key is used for in stream cipher system applied for image data. The properties like, uniformity, independence and maximum length for the word oriented non binary key sequence is tested and verified. The security issues of cipher systems using these key sequences for an image is also tested and evaluated for its strength.