时间： 2017.12.26（星期二）上午10:00

地点：信工所第三研究室4303会议室

报告人：Khoa Nguyen

Khoa Nguye, a Senior Research Fellow at Division of Mathematical Sciences(MAS),School of Physical and Mathematical Sciences(SPMS),Nanyang Technological University (NTU). His research interests are in the areas of cryptography and information security. Currently, he is particularly interested in privacy-enhancing cryptographic protocols based on intractability assumptions from lattices and codes.

题目：Zero-knowledge arguments for lattice-based PRFs and applications to E-cash

摘要：Beyond their security guarantees under well-studied assumptions, algebraic pseudo-random functions are motivated by their compatibility with efficient zero-knowledge proof systems, which is useful in a number of privacy applications like digital cash. We consider the problem of proving the correct evaluation of lattice-based PRFs based on the Learning-With-Rounding (LWR) problem introduced by Banerjee et al. (Eurocrypt'12). Namely, we are interested zero-knowledge arguments of knowledge of triples(y,k,x)such that y=F_k(x)is the correct evaluation of a PRF for a secret input x and a committed key k. While analogous statements admit efficient zero-knowledge protocols in the discrete logarithm setting, they have never been addressed in lattices so far. We provide such arguments for the key homomorphic PRF of Boneh et al. (Crypto'13) and the generic PRF implied by the LWR-based pseudo-random generator. As an application of our ZK arguments, we design the first compact e-cash system based on lattice assumptions. By “compact”, we mean that the complexity is at most logarithmic in the value of withdrawn wallets. Our system can be seen as a lattice-based analogue of the first compact e-cash construction due to Camenisch, Hohenberger and Lysyanskaya (Eurocrypt'05).