Modified Hill Cipher Algorithm using Myszkowski Transposition to address Known-Plaintext attack

Abstract

Abstract: Hill Cipher algorithm is a Polygraphic cipher known to be vulnerable to the Known-Plaintext attack. It is a type of attack wherein the attacker has access to a pair of Plaintext and Ciphertext. Possible leaked information can be used to reveal critical data which can include the private key that is used in the encryption of the plaintext. In this study, the researchers propose an improved scheme by incorporating Myszkowski transposition in the algorithm to address the specified problem. Runtime Test and Statistical test such as the Avalanche effect were used to evaluate the performance of the algorithm. The test yielded a 25.70% faster runtime based on previous modifications and a 52.78% Avalanche Effect. Randomness test such as the Monobit test, Runs Test and Longest Run of Ones in a Block test were applied to evaluate the ciphertext produced. The criterion for the Randomness Test requires its p-value to be greater than 0.01, the evaluation showed a 0.249, 0.167 and 0.368 p-value, respectively. The proposed scheme proved that the algorithm is cryptographically secure and efficient as all tests yielded favorable results. Keywords: Cryptography, Hill Cipher, Encryption, Decryption, Key Generation