With the development of information technology, information security as well as the implementation of encryption systems becomes more and more complex, and therefore new methods are explored to simplify the complexity of the implementation. Cellular automata (CA) have the characteristics of simplicity of basic components, locality of CA interactions, massive parallelism of information processing, and exhibiting of complex global properties, which make them suitable for cryptography applications. Based on the reversible CA with input boundary, a new method of encryption is presented in this paper, the key of the new method consists of the reversible CA, the vectors input from the input boundary, and the number of iterations. Evidently, it has a larger key space than other methods with only the reversible CA itself as the key.