Abstract: Chaotic mapping can produce chaotic sequence easily. Applying the features of chaos for data security communication in Internet has various advantages. In this article, we discuss the data encryption and decryption of multi-format images and files with stream cipher produced by chaotic mapping so that computer can recognize and display the images and files correctly after decryption. This method overcomes the limitation of data encryption and decryption merely for single-format image or file, and shows the strong feasibility in practice.