Abstract

Security in transmission and storage of digital images has its importance in today's military image communications and confidential video conferencing. The Hill cipher algorithm is one of the symmetric key algorithms that have several advantages in data encryption. However, a drawback of the algorithm is its weakness security that can be easily broken with a known plaintext attack. This is mainly due to the fact that the encryption provide just a linear transformation (blocks linear dependency ). In this paper, we modify the Hill cipher algorithm to give high level security by adjusting the key matrix to allow high security and better image encryption. The security analysis of the modified algorithm proves its robustness against a known plaintext attack. Experimental results show that the modified algorithm yields significantly superior image encryption quality when it is compared to the original one.

Keywords: Hill cipher, Image encryption, Modified Hill cipher, Quality of encryption.