Please note: This PhD seminar will be given online.
Sebastian
Reynaldo
Verschoor,
PhD
candidate
David
R.
Cheriton
School
of
Computer
Science
Supervisor: Professor Michele Mosca
Secure messaging applications establish a secured channel between two long-term public keys. Additional key authentication ensures to users that these public keys actually belong to the intended parties, prevent attacks such as a person-in-the-middle. Off-the-Record messaging provides a unique solution in the form of the socialist millionaire protocol (SMP), allowing user-friendly in-band key authentication based on a low-entropy secret between users. This solution uses Diffie-Hellman and other discrete logarithm based primitives and is therefore vulnerable to quantum attacks using Shor’s algorithm.
I propose a post-quantum replacement for the SMP, based on techniques from private set intersection. The protocol builds (a version of) a private equality test from oblivious transfers, which in turn are constructed from post-quantum key encapsulation mechanisms. I give a security argument in the simple universal composability framework, and I provide a prototype implementation in C to demonstrate the solution is practical. In the talk I give an overview of the protocol construction and discuss the considerations that lead to the current solution.
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