Unbounded Non-Malleable Non-Interactive Zero Knowledge Protocols for NP

In asynchronous network communication, non-malleability is requiredto resist against man-in-the-middle attack. Based on the existenceof one-way permutation, we propose two unbounded non-malleableNon-interactive zero knowledge (NIZK) protocols. Firstly, by usingNIZK argument of knowledge instead of as abuilding block, we transform 5-rounds concurrent non-malleable zeroknowledge argument in the Common reference string (CRS)model15 to non-malleable NIZK argument. The transformationachieves optimal round efficiency in the same model. Secondly, wesimplify the second scheme in CRYPO'018 by using thetechnique hidden unduplicatable set selection. In thesimplified scheme, the CRS is much shorter and statements to beproved in the two NIZK sub-protocols are simplified.