Seminar on Security of Embedded Electronic Systems

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Thomas Pöppelmann

Lattice-based post-quantum key exchange for TLS (a new hope)

At IEEE Security & Privacy 2015, Bos, Costello, Naehrig, and Stebila proposed an instantiation of Peikert's ring-learning-with-errors--based (Ring-LWE) key-exchange protocol (PQCrypto 2014), together with an implementation integrated into OpenSSL, with the affirmed goal of providing post-quantum security for TLS. In this talk I will present joint work with Alkim, Ducas, and Schwabe, in which we revisit their instantiation and stand-alone implementation. Specifically, we propose new parameters and a better suited error distribution, analyze the scheme's hardness against attacks by quantum computers in a conservative way, introduce a new and more efficient error-reconciliation mechanism, and propose a defense against backdoors and all-for-the-price-of-one attacks. By these measures and for the same lattice dimension, we more than double the security parameter, halve the communication overhead, and speed up computation by more than a factor of 9 in a portable C implementation and by more than a factor of 24 in an optimized implementation targeting current Intel CPUs. These speedups are achieved with comprehensive protection against timing attacks.