Re: ‘Secretbook’ Lets You Encode Hidden Messages in Your Facebook Pics

[Ian Batten]

On 11 Apr 2013, at 11:56, Richard Clayton <richard at highwayman.com> wrote:
> 
> The particular proposal here seems to have been specifically designed to
> survive Facebook's transform rather than to survive more general changes
> to the image.

Which is an endless arms race, of course.  If Facebook, or people who might lean on Facebook, decide to perturb pictures in such a way that steganography is corrupted, then there are a limitless number of ways that might be done.  Especially if the photographs are assumed to only be displayed on screen, rather than used for critical editing and enlarged printing.  You can propose a method of steganography which passes today's transformation, and as soon as the method is out there, the transformation can be changed to break it.

What would be interesting, but a rather more substantial piece of work (to put it mildly), would be a technique which is demonstrably robust in the face of any transformation which preserves specific properties of the image, while also being undetectable in the same use.  Rather than being proof against particular transformations, it would be proof against all transformations other than those which visibly break the images.  That would break the cycle of the arms race.

ian