Self-Invertible Key on Cipher Polygraphic Polyfunction with Eigen Matrix based IMIE

Hill Cipher’s System and its modifications are still practiced mainly in sending a secret message involving images. One drawback that the recipient of the message is trying to overcome is to get the decryption key from the cipher text to plain text during the decryption process. Previous studies have proven that using self-invertible keys can reduce the computation cost to obtain this key. This paper generates a self-invertible matrix based on Integer-Entry Matrix with all Integer Eigenvalues (IMIE). Subsequently, we executed it into Cipher Polygraphic Polyfunction Cryptosystem and observed the effect.