Researchers Calculate Capacity of a Steganographic Channel

KentuckyFC writes "Steganography is the art of hiding a message in such a way that only the sender and receiver realize it is there. (By contrast, cryptography disguises the content of a message but makes no attempt to hide it.) The central problem for steganographers is how much data can be hidden without being detected. But the complexity of this problem has meant it has been largely ignored. Now two computer scientists (one working for Google) have made a major theoretical breakthrough by tackling the problem in the same way that the electrical engineer Claude Shannon calculated the capacity of an ordinary communications channel in the 1940s. In Shannon's theory, a transmission is considered successful if the decoder properly determines which message the encoder has sent. In the stego-channel, a transmission is successful if the decoder properly determines the sent message without anybody else detecting its presence (abstract). Studying a stego-channel in this way leads to some counter-intuitive results: for example, in certain circumstances, doubling the number of algorithms looking for hidden data can increase the capacity of the steganographic channel"

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[xmarkd400x]

In the stego-channel, a transmission is successful if the decoder properly determines the sent message without anybody else detecting its presence (abstract).

When my girlfriend is talking on the phone, I am almost never aware that a message is being sent. She is so effective, in fact, that often when I am the intended recipient I am not aware that a message is being sent!

Re:Were's Waldo's message?

[Anonymous Coward]

stegan O graphy i S T he a R t of hiding A message in su C h a way that only the sender and receiver realize it is there. (by contrast, cryptography disg U i S es the content of a message but makes no attempt to h I de it.)

there' S a secret messa G e in this post. c A n an Y one find it?

Re:Need for steganography

[Ngarrang]

Do we need to hide crypto anymore?

Yes. There are many places in this world where freedom of information is oppressed. Having a method of communicating in the clear without raising any red flags is a Good Thing(tm).

For example, let's say you are an evil political dissident in China, trying to spread ideas of democracy and capitalism. If you send an encrypted message to your corrupt imperialist American ally, that seems suspicious. If you have nothing to hide, then why are you hiding it?

But, if you can send your friend a message about how you are growing corn in relatively poor conditions and how great the local government has been in supporting the effort...with a stego message hidden inside, then that is probably going to slip right through.

The best way to not get caught is to look like there is nothing to catch.