Key Matrix Generation Techniques for Hill Cipher Cryptosystem – A Comparative Study

Summary

Hill cipher cryptosystem is a linear algebra‐based classical polygraphic substitution cipher‐based technique. If the encryption key matrix (also called the key matrix) is not invertible, obtaining the de‐ crypted text from the encrypted text is not possible. This is because the key matrix must follow some criteria for decryption to be possible: The encryption key matrix must be invertible with respect to the modulo number. If the key matrix is generated randomly, there is a possibility that the key matrix's inverse does not exist. This paper attempts to compare two new techniques for generating the key matrix for the hill cipher cryptosystem. The proposed algorithm has been developed keeping consideration of security aspects, performance of the generated key matrix, ease of implementation, and limitations. A comparative study has been performed by utilizing a key matrix generation for Hill Cipher using Magic Rectangle (KMGHCMR)” and “Novel Methods of Generating a Self‐Invertible Matrix for Hill Cipher (NMGSIMHC).”