Multi-operation data encryption mechanism using dynamic data blocking and randomized substitution

Abstract

Existing cryptosystems deal with static design features such as fixed sized data blocks, static substitution and apply identical set of known encryption operations in each encryption round. Fixed sized blocks associate several issues such as ineffective permutations, padding issues, deterministic brute force strength and known-length of bits which support the cracker in formulating of modern cryptanalysis. Existing static substitution policies are either not optimally fit for dynamic sized data blocks or contain known S-box transformation and fixed lookup tables. Moreover, static substitution does not directly correlate with secret key due to which it has not been shown safer especially for Advanced Encryption Standard (AES) and Data Encryption Standard (DES). Presently, entire cryptosystems encrypt each data block with identical set of known operations in each iteration, thereby lacked to offer dynamic selection of encryption operation. These discussed, static design features are fully known to the cracker, therefore caused the practical cracking of DES and undesirable security pitfalls against AES as witnessed in earlier studies. Various studies have reported the mathematical cryptanalysis of AES up to full of its 14 rounds. Thus, this situation completely demands the proposal of dynamic design features in symmetric cryptosystems. Firstly, as a substitute to fixed sized data blocks, the Dynamic Data Blocking Mechanism (DDBM) has been proposed to provide the facility of dynamic sized data blocks. Secondly, as an alternative of static substitution approach, a Randomized Substitution Mechanism (RSM) has been proposed which can randomly modify session-keys and plaintext blocks. Finally, Multi-operation Data Encryption Mechanism (MoDEM) has been proposed to tackle the issue of static and identical set of known encryption operations on each data block in each round. With MoDEM, the encryption operation can dynamically be selected against the desired data block from the list of multiple operations bundled with several sub-operations. The methods or operations such as exclusive-OR, 8-bit permutation, random substitution, cyclic-shift and logical operations are used. Results show that DDBM can provide dynamic sized data blocks comparatively to existing approaches. Both RSM and MoDEM fulfill dynamicity and randomness properties as tested and validated under recommended statistical analysis with standard tool. The proposed method not only contains randomness and avalanche properties but it also has passed recommended statistical tests within five encryption rounds (significant than existing). Moreover, mathematical testing shows that common security attacks are not applicable on MoDEM and brute force attack is significantly resistive.