How does Steganography work?
I interviewed a friend at the NSA to help me understand how content can be added to files in a covert way without noticeably changing or degrading the original. I also asked about the government’s use of steganalysis and academic work on steganalysis, more on that topic in subsequent posts.
Understanding steganography requires at least a cursory knowledge of mathematics, binary, and the characteristics of popular file types like jpeg. Using steg to convey information covertly doesn’t require any of this. Google and wikipedia have more than enough information to help even the least technical person encrypt a file.
Insert more later…. left my notes at work….
Channels: The easiest channel for creating steg files is static digital images. JPEGs, for example, are large files with a great deal of repetitive content. Audio, video, and text files are more difficult to encrypt without noticeably degrading the file. One technique for adding steg to audio files adds covert information to the background or “white noise” on an original audio file. While encrypting audio, video, and text files is more difficult, fewer techniques exists for detecting steg files using these channels.