A more efficient computationally sound non-interactive zero-knowledge shuffle argument

We propose a new non-interactive perfect zero-knowledge (NIZK) shuffle argument that, when compared with the only previously known efficient NIZK shuffle argument by Groth and Lu, has a small constant factor times smaller computation and communication, and is based on more standard computational assumptions. Differently from Groth and Lu who only prove the co-soundness of their argument under purely computational assumptions, we prove computational soundness under a necessary knowledge assumption. We also present a general transformation that results in a shuffle argument that has a quadratically smaller common reference string (CRS) and a small constant factor times longer argument than the original shuffle. This can be interpreted as a general technique of decreasing the offline cost of an arbitrary shuffle argument.