Life is about to become more difficult for countries trying to censor access to foreign websites. A system dubbed Collage will allow users in these countries to download stories from blocked sites while visiting seemingly uncontroversial sites such as Flickr.

Collage relies on a well-established technique known as digital steganography, in which an image file is changed to encode the hidden message without obviously affecting the appearance of the image. A prototype version is due to be unveiled on Friday, 13 August.

Steganography normally requires specialist software, but Collage is designed so that anti-censorship activists and readers can publish and download the hidden stories without any specialist skills. A publisher or activist can, for example, use Collage to copy news stories from a website and embed the articles into Flickr images in a process that is almost entirely automated.

In the prototype, stories from the BBC news site are used, but in principle any web content could be hidden. Collage can hide as many as 15 news articles in just seven medium-sized Flickr images.


News feeds

Once the material is embedded in a Flickr image, anyone with Collage can download it and extract the stories. A censor attempting to monitor traffic from a prohibited site would only see the reader visiting Flickr, which is not generally blocked by web censors.

Collage is able to identify which images have been used to hide material. All the would-be reader has to do is click on the date they are interested in; the stories appear a few minutes later. “It all happens in the background,” says Sam Burnett at the Georgia Institute of Technology in Atlanta, part of the team behind Collage.

Burnett has designed a Flickr upload tool that links with Collage and embeds content that publishers or activists want to make available.

Collage can also be easily extended so that stories are embedded in other photo-sharing sites. The idea is to spread material across numerous sites that host user-generated content so that the activity of someone running Collage appears much like that of any internet user and the censors cannot just block access to Flickr. Collage does, however, rely on the goodwill of Flickr users, who will have to provide access to the images where the articles are to be hidden.

Burnett is relying on opposition to censorship to motivate people to use Collage. “We’re betting on people getting a warm fuzzy feeling because they are beating censorship,” he says.

To coincide with the launch of the prototype, Burnett will present a paper on the system at the USENIX Security Symposium in Washington DC.