JSteg: Steganography and Steganalysis

1.Introduction: Steganography is the art and science of hiding communication; a steganographic system thus embeds hidden content in unremarkable cover media so as not to arouse an eavesdropper’s suspicion. In the past, people used hidden tattoos or invisible ink to convey steganographic content. Today, computer and network technologies provide easy-to-use communication channels for steganography. Essentially, the information-hiding process in a steganographic system starts by identifying a cover medium’s redundant bits (those that can be modifiedwithout destroying that medium’s integrity).1 The embedding process creates a stego medium by replacing these redundant bits with data from the hidden message. Modern steganography’s goal is to keep its mere presence undetectable, but steganographic systems— because of their invasive nature—leave behind detectabletraces in the cover medium. Even if secret content is not revealed, the existence of it is: modifying the cover medium changes its statistical properties, so eavesdroppers can detect the distortions in the resulting stego medium’s statistical properties. The process of finding these distortions is called statistical steganalysis.