Steganography with Flickr.

Keith McDuffee, my colleague over at TUAW fledgeling sister blog The Digital Photography Weblog, posted an article the other day about using steganography with Flickr. Steganography, for those of you who haven't come across it before, is the art of hiding one kind of information inside a different kind of information. The most famous forms of steganography are probably the microdots used by WWII German spies and those crazy Magic Eye pictures that were so popular in the 1990's. One current steganographic practice is to use the "empty" space in lossy compression schemes like JPEG and MP3 to hide digital watermarks in pictures and audio files. You can, though, use "stego" programs to hide any data you want, and Keith has been using Flickr to back up some files. He uses steghide, which is a standard program on most Linux installations, but compiling it on OS X can be tricky and neither Fink or DarwinPorts seem to have it at the moment. You'll probably want to check out Pict Encrypt or another Mac specific option. Just make sure your finished file comes in under the 10MB Flickr file size limit, or your data will get munged when Flickr resizes the file.