As more and more data is stored on computers and transmitted over networks, it`s no surprise that steganography has entered the digital age. On computers and networks, steganography applications allow someone to hide any type of binary file in any other binary, although image and audio files are the most common media today. In a model of pure steganography, William knows nothing about Alice and Bob`s steganography method. This is a bad assumption of Alice and Bob, because obfuscation security rarely works and is particularly disastrous when applied to cryptography. However, it is often the model of the digital forensic analyst who scans a website or hard drive for the eventual use of steganography. There are currently more than 100 steganography programs, ranging from free downloads to commercial products. This section presents some simple examples of steganography by hiding an 11,067-byte GIF map of Burlington, Vermont Airport (Figure 5) in GIF, JPEG, and WAV files. The prisoner problem (Simmons 1983) is often used to describe steganography, although it was originally introduced to describe a cryptography scenario. The problem concerns two prisoners, Alice and Bob, who are locked in separate cells and want to tell each other a secret plan. Alice and Bob are allowed to exchange messages with each other, but William, the supervisor, can read all the messages.
Alice and Bob know that William will end communication if he discovers the secret channel (Chandramouli 2002; Fridrich et al., 2003B). Provos, N. and Honeyman, P. Hide and seek: An introduction to steganography. IEEE Security & Privacy (2003) 1(3):32-44. Also available: niels.xtdnet.nl/papers/practical.pdf. The second important function of steganography detection software is to find possible carrier files. Ideally, the detection software should also give some clues about the steganography algorithm used to hide information in the suspicious file, so that the analyst may be able to try to retrieve the hidden information. Steganography has a number of harmful uses; in particular, concealing records of illegal activities, financial fraud, industrial espionage, and communications between members of criminal or terrorist organizations (Hosmer and Hyde, 2003). Dartmouth College, Institute for Security Technology Studies.
New software to detect hidden messages in digital images [Online]. (2003, December 29). Available: www.ists.dartmouth.edu/text/steganography.php. It is impossible to know how widespread the use of steganography is by criminals and terrorists (Hosmer & Hyde, 2003). However, today`s truth may not matter. The use of steganography is certain to increase and be a growing barrier to law enforcement and counter-terrorism efforts. Ignoring the importance of steganography due to lack of statistics is “security by denial” and is not a good strategy. Steganography offers very useful and commercially important features in the digital world, especially digital watermarks. In this application, an author can embed a hidden message in a file so that intellectual property can be claimed later and/or to ensure the integrity of the content. For example, an artist could publish original artwork on a website. If someone else steals the file and claims the work as their own, the artist can later prove ownership, as only he can restore the watermark (Arnold et al. 2003; Barni et al., 2001; Kwok, 2003).
Although conceptually similar to steganography, digital watermarking usually has different technical purposes. In general, only a small amount of repetitive information is inserted into the carrier, there is no need to hide the watermark information, and it is useful that the watermark can be removed while maintaining the integrity of the carrier. The difficulty of the supervisor`s task depends largely on the complexity of the steganography algorithm and the extent of William`s prior knowledge (Chandramouli 2002; Fridrich et al., 2003B; Provos and Honeyman, 2003). And the same cycle repeats itself that in the world of cryptography, bridge analysis helps in the search for integrated steganography but also shows authors new steganography algorithms how to avoid detection. The last example uses S-Tools, a program by Andy Brown that can hide information in GIF, BMP and WAV files.