The susceptibility of conventional Caesar cipher as a tool for encryption is a known fact not only due to its simplicity but also its practical infeasibilities. The requirement in today's complex age is of a method which has higher effectiveness in terms of being immune to cryptanalysis and at the same time is simple to implement. This paper is about a distinctive methodology by incorporation of a scheme that combines the use of dynamically generated keysets from grayscale images and a modified cipher. The unique aspect proposed yields higher security as each keyset derives its key values from the respective grayscale image which are used iteratively in the modified algorithm. Every iteration in the algorithm makes use of a different key value from the keyset, producing a new cipher-text in each iteration. Cipher-text produced in every iteration is encrypted in the succeeding iteration. This process repeats until all key values are used to obtain a highly-encrypted form of cipher-text. Hence, this sequential and iterative approach is proposed as an effective solution for present-day requirements of information security.

Iterative Caesar cipher using grayscale image pixel values as keys

Ever since the evolution of time, there have been changes in the transmission and storage of images, but the only constants are the security issues that came along. Eavesdropping is the major pivotal security challenge and throughout the evolution of time even though many encryption methods are developed, the middlemen and hackers etc. also developed new methods, simultaneously, to sniff the information. In this process of eavesdropping, there are many different methods like chosen-cipher text attack, brute force attack etc. In order to cope up with these deficiencies, we proposed an improvised version of the Elliptical curve cryptography (ECC) with multiple keys generated by fractals. Keys which are generated by the combination of ECC and Fractals are used for the conversion of the symmetric Hill Cipher encryption to asymmetric, which has higher security. In order to measure the efficiency of proposed algorithm we have used the entropy, peak to signal noise ratio(PSNR), unified average changing intensity(UACI) and the correlation between pixels along horizontal, vertical and diagonal directions.

Roopesh Gamini

Papers

Elliptical Curve Cryptography for Images Using Fractal Based Multiple Key Hill Cipher