Jincheng Zhuang

Qi Cheng, Jun Zhang, Jincheng Zhuang

The Ring Learning-With-Errors (LWE) problem, whose security is based on hard ideal lattice problems, has proven to be a promising primitive with diverse applications in cryptography. There are however recent discoveries of faster algorithms for the principal ideal SVP problem, and attempts to generalize the attack to non-principal ideals. In this work, we study the LWE problem on group rings, and build cryptographic schemes based on this new primitive. One can regard the LWE on cyclotomic integers as a special case when the underlying group is cyclic, while our proposal utilizes non-commutative groups, which eliminates the weakness associated with the principal ideal lattices. In particular, we show how to build public key encryption schemes from dihedral group rings, which maintains the efficiency of the ring-LWE and improves its security.

Qi Cheng, Daqing Wan, Jincheng Zhuang

In the recent breakthrough paper by Barbulescu, Gaudry, Joux and Thom{é}, a quasi-polynomial time algorithm (QPA) is proposed for the discrete logarithm problem over finite fields of small characteristic. The time complexity analysis of the algorithm is based on several heuristics presented in their paper. We show that some of the heuristics are problematic in their original forms, in particular, when the field is not a Kummer extension. We believe that the basic idea behind the new approach should still work, and propose a fix to the algorithm in non-Kummer cases, without altering the quasi-polynomial time complexity. The modified algorithm is also heuristic. Further study is required in order to fully understand the effectiveness of the new approach.