An Improved Hill Cipher Algorithm using CBC and Hexadecimal S-Box

In order to ensure the security and confidentiality of data, cryptography is used during the exchange of information. The hill cipher is a polygraph cipher with a basic structure and easy calculations. Nonetheless, it is vulnerable to a known-plaintext attack. The instability of an invertible key matrix for decryption is another drawback. In this paper, the method of encrypting plaintext in 128-bit blocks using multiple rounds of encryption process, cipher block chaining, and hexadecimal substitution box was used to resolve these limitations of the Hill cipher. The modified approach offers better data protection and overcomes the drawbacks of the original hill cipher algorithm. The test results prove that the ciphertext protection is 55.34 percent avalanche effect score and goes through the randomness check method based on the actual experiment.