This paper studies the security of an image encryption scheme based on the Hill cipher and reports its following problems: 1) there is a simple necessary and sufficient condition that makes a number of secret keys invalid; 2) it is insensitive to the change of the secret key; 3) it is insensitive to the change of the plain-image; 4) it can be broken with only one known/chosen-plaintext; 5) it has some other minor defects.
@article{arxiv.0712.0693,
title = {Cryptanalysis of an image encryption scheme based on the Hill cipher},
author = {Chengqing Li and Dan Zhang and Guanrong Chen},
journal= {arXiv preprint arXiv:0712.0693},
year = {2009}
}