Where do you go to get uncensored news stories? Google News? Wikileaks? Well, how about Flickr?
Yes, that’s right, the photosharing site could soon be the place to go to read news stories without the detection of hostile governments. A system known as Collage, which will become publicly available on Friday, allows users to hide text content within an image.
The technique is simply the latest digital incarnation of steganography, the art of hiding a message in a way that makes it difficult to detect that it even exists. (Early techniques ranged from good old-fashioned invisible ink to the somewhat less convenient trick of shaving a slave’s head, tattooing a message on their skull, waiting for their hair to grow back, then sending them off to the recipient.)
The precise method used by Collage appears to be under wraps, but there are several existing techniques. One is to conceal tiny objects in an image, with the positioning of the objects translating to the information. Another is to hide one image in the two lowest bits in each color component of another image, as shown in the pictures above where the right-hand picture is concealed, at low brightness, within the left-hand image.
The big difference with Collage is that users don’t need any technical knowledge of the technique to consult the embedded information. The people sending the message can use an upload tool that embeds the news stories in Flickr images automatically. Then, those who want to read the message simply use the software to click on a publication date, at which point Collage retrieves all the relevant Flickr images and decodes the date.
At first the system will work on the basis that readers will only need to access Flickr, which isn’t generally blocked by government censors in the same way as news sites. However, the option is open to extend it to other image-based sites if Flickr winds up on a block list.
Sam Burnett of the Georgia Institute of Technology, part of the team behind Collage, will present a paper on the technique at the USENIX security event in Washington DC today. He says testing shows the system works well enough to hide two news stories in a medium-sized image.
