Lattice gas cellular automata (Lgca) are particular cellular automata that imitate the behavior of par- ticles moving on a lattice. We used a particular set of Lgca rules, called hpp, to mix bits in data blocks and obtain a symmetric cryptographic algorithm. The encryption and decryption keys are the positions of perturbation sites on the lattice (walls). Basically, this paper presents an original way to perform cryp- tographic operations, based on cellular automata. In this paper, we show several characteristics about our algorithm: typical block size (2^(2n-1) ), key-length (2^n ), number of rounds (2^(n+1) ). We also evaluate avalanche and strict avalanche properties with respect to key and plain text. Finally, we highlight the underbellies of our method and give clues to solve them.