Hill cipher algorithm using two keywords and 94 ASCII characters

Abstract

Hill Cipher algorithm is one of the methods in cryptography. The Hill Cipher algorithm was invented by Lester S. Hill in 1929. The Hill Cipher algorithm uses 1 keyword and 26 characters in the alphabet. The number of keywords and characters affect the strength of the Hill Cipher algorithm. In this study, modifications to the Hill Cipher algorithm were carried out using 2 keywords and 94 ASCII Characters with the aim of increasing the strength of the Hill Cipher algorithm. The modification technique used is to multiply the matrix of 2 keywords, replace 26 characters in the alphabet into 94 ASCII Characters, change the ciphertext equation to C = (K1K2)P(mod 94) and change the plaintext equation to P = ((K1K2)-1 mod 94)C(mod 94). As a result, this modification can be done and the Hill Cipher algorithm can work well in encoding messages.