Comment on ‘Targeted Ciphers for Format‐Preserving Encryption’ from Selected Areas in Cryptography 2018

Abstract

Format-preserving encryption (FPE) allows encrypting plaintexts while preserving a specific format. In Selected Areas in Cryptography 2018, two targeted ciphers were proposed as new FPE schemes. The second scheme was designed with an algorithm called Mix-Swap-Unmix that is shown to be equivalent to a particular matching exchange process under a specific setting. In this comment paper, we prove that the matching exchange process is invalid. As a result, this equivalence does not exist. The matching exchange process is proposed by Czumaj and Kutyłowski to permute items at random in parallel andThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.