Here's an application which is well suited for steganography. This is a random-character stereogram. Look at it with a monospace font and unfocus your eyes so the two blocks of text merge, and you will see the message HI displayed: VGhpcyBpcyBhIHRlc3Qg VGhpcyBpcyBhIHRlc3Qg bWVzc2FnZSB3aGljaCBp bWVc2AFnZB3xaGljaCBp cyBiZWluZyBzZW50IHZp cyBZWmluZBzvZW50IHZp YSBzdGVnYW5vZ3JhcGh5 YSBdGVnYW5v9Z3JhcGh5 LgpIYWQgdGhpcyBiZWVu LgpYW1QgdhpBcyBiZWVu IGFuIGFjdHVhbCBtZXNz IGFIGoFjdVhXbCBtZXNz YWdlLCBpdCB3b3VsZCBo YWdlLCBpdCB3b3VsZCBo YXZlIGJlZW4gZW5jcnlw YXZIGJlZW4vgZW5jcnlw dGVkCnVzaW5nIGEgbWV0 dGVkCVzaUW5nIGEgbWV0 aG9kIHdoaWNoIHByb2R1 aG9kIdoa4WNoIHByb2R1 Y2VzIG91dHB1dCB3aGlj Y2VzI91dAHB1dCB3aGlj aCBpcyBpbmRpc3Rpbmd1 aCBcyBpbmRnpc3Rpbmd1 aXNoYWJsZQpmcm9tIHJh aXNoYWJsZQpmcm9tIHJh bmRvbSBieXRlcy4K bmRvbSBieXRlcy4K This was just done manually, so it's pretty crude. It would be easy to write a program to display any message desired. People could get in the habit of sending long vertical stereograms saying "GO GIANTS" or "MICROSOFT SUX" or whatever they felt like at the moment. The program could either generate its own random numbers or else suck in random data from a disk file. In this case, if you take the left block and reformat it so that it can be base64 decoded, you will see a short message. (Unix users can pass the left block through "mimencode -u".) In a real stego application the message would be encrypted in 'stealth' form so it was indistinguishable from random bits to anyone who did not hold the decryption key. This could even catch on as a legal "thumb your nose at the spooks" fad, people adding random sterograms at the end of their messages. You could even have an active .sig which had a constant message but used different random characters each time. They wouldn't actually be sending anything but there would be no way to be sure. Some people say they'll just forbid transmitting data that looks random, but realistically, that would be very unlikely to happen.