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> While it might be impossible to guarantee security for text created by humans, a new proof lays out for the first time how to achieve perfect security for ste
by truculent 3y ago
> While it might be impossible to guarantee security for text created by humans, a new proof lays out for the first time how to achieve perfect security for steganography in machine-generated messages — whether they’re text, images, video or any other media. The authors also include a set of algorithms to produce secure messages, and they are working on ways to combine them with popular apps.
This seems both novel and non-trivial to me (admittedly not a cryptographer)
- pseudo0 3y agoIt's interesting from a theoretical perspective, but the novelty relies on using a really strong definition of security: > In this work, we consider the information-theoretic model of steganography introduced in (Cachin,1998). In Cachin (1998)’s model, the exact distribution of covertext is assumed to be known to all parties. Security is defined in terms of the KL divergence between the distribution of covertext and the distribution of stegotext. A procedure is said to be perfectly secure if it guarantees a divergence of zero. In a practical scenario, the attacker likely does not know the distribution of covertext and therefore cannot detect a theoretically imperfect steg implementation. It's an area where the steg user has a huge advantage, as there are a practically infinite number of ways to do steganography and it's non-trivial to even detect that it is being used in the first place. And if you obtain the covertext distribution by say hacking the computer generating the steg, then why not just exfiltrate the plaintext directly?