Backdooring encryption algorithms is considered as the best way to enforce cryptographic control. Until now, only implementation backdoors (at the protocol/implementation/management level) are generally considered. In this paper we propose to address the most critical issue of backdoors: mathematical backdoors or by-design backdoors, which are put directly at the mathematical design of the encryption algorithm. While the algorithm may be totally public, proving that there is a backdoor, identifying it and exploiting it, may be an intractable problem.
By Eric Filiol & Arnaud Bannier
Full Abstract & Presentation Materials: https://www.blackhat.com/eu-17/briefings.html#by-design-backdooring-of-encryption-system-can-we-trust-foreign-encryption-algorithms