Steganography in HTML based on substitution of script codes

The HTML document is a main kind of public resources in the Internet, while the research in the steganography and steganalysis of them are in the infancy. In this paper, we propose a novel steganography in HTML documents. Different from natural language text, HTML documents have plentiful script codes which can be utilized for covert transmission more easily than the common text. The syntax structures of programming languages are strict and precise, so to generate scripts that are different in text but strictly equivalent in lexeme is possible. In the steganography, based on the substitution of variables and function naming, covert bits are successfully embedded with no script errors. Because of the transparency and flexibility of script codes, the well-disguised stego-HTML document has a legitimate appearance that is imperceptible. In the experiment, the embedding efficiency of the technique is considerable, proving that the steganography is feasible and promising.