Proof of plaintext knowledge for code-based public-key encryption revisited

Abstract

In a recent paper at Asiacrypt'2012, Jain et al point out that Veron code-based identification scheme is not perfect zero-knowledge. In particular, this creates a gap in security arguments of proof of plaintext knowledge (PPK) and verifiable encryption for the McEliece public key encryption (PKE) proposed by Morozov and Takagi at ACISP'2012. We fix the latter result by showing that PPK for the code-based Niederreiter and McEliece PKE's can be constructed using Stern zero-knowledge identification scheme, which is unaffected by the above mentioned problem. Since code-based verifiable encryption uses PPK as a main ingredient, our proposal presents a fix for the McEliece verifiable encryption as well. In addition, we present the Niederreiter verifiable encryption.