Universiti Sains Malaysia
The Hill cipher is the first polygraph cipher which has some advantages in symmetric data encryption. However, it is vulnerable to known plaintext attack. Another setback is that an invertible key matrix is needed for decryption and it is not suitable for encrypting a plaintext consisting of zeroes. The objective of this work is to modify the existing hill cipher to overcome these three issues. Studies on previous paper showed that the existing hill algorithms are not yet sufficient. Some of these algorithms are still vulnerable to known plaintext attack. On the other hand, some of these algorithms have better randomization properties and as a result they are more resistant against known plaintext attack.