The Reverse Engineering of Reverse Encryption Algorithm and a Systematic Comparison to DES

The field of Cryptography has developed by numerous incidents of proposed new Algorithms, their verification and their subsequent cryptanalysis. This paper provides a novel approach to verify the structural and functional correctness of a cryptographic algorithm with implicit recovery of the model into an extended finite state machine. The proposed method is used to analyze one particular algorithm proposed in the past with the name Reverse Encryption Algorithm (REA). On critical analysis based on Shannon's principle of confusion and diffusion, The REA algorithm fails to qualify as a symmetric key encryption algorithm. The decryption algorithm is simply found to be a non-key reverse transformation of Ciphertext and therefore the performance of REA algorithm cannot be compared with the DES or any other well proven algorithm used in the cryptography. The reported performance comparison also seems to be meaningless as the most of the time of REA algorithm is wasted in performing the ASCII, BINARY and REVRSE operations while there is no application of confusion and diffusion logic, which makes it vulnerable for primitive Cryptanalysis. The purpose of the paper is to develop a framework for verification of correctness of the encryption and decryption algorithms, and apply the framework to prove the structural and functional validly of the REA algorithm as a case study.