Cryptography has become a basic requirement in this age of global electronic connectivity to secure data storage and transmission against the possibility of message eavsdropping and electronic fraud. In this article, we describe a single key crypto-graphic system based on one- and two-dimensional non-uniform cellular automata randomizers obtained by artificial evolution. The robustness of the scheme against cryptanalytic attacks is discussed and it is shown that direct cryptanalysis requires an exponentially growing amount of computational resources. The advantage of implementing the proposed scheme in hardware for high-speed operation is also discussed.