Paper 2020/1200

WBCD: White-box Block Cipher Scheme Based on Dynamic Library

Yatao Yang, Ye Zhang, Yuying Zhai, Zheng Yuan, and Guangwu Xu

Abstract

The aim of white-box cryptography is to protect a secret key in a whitebox environment in which an adversary has full control ability over the computer’s execution process and the running environment. In order to solve the issues of lower security in static white-box algorithm and inconvenient application in traditional dynamic white-box algorithm, it is proposed that a white-box block cipher scheme based on dynamic library named WBCD. In this scheme, look-up tables and affine transformations are used to construct dynamic white-box library, which ensure that the different look-up tables can be used for each round of encryptions. In order to illustrate the effectiveness of WBCD, it is designed a novel white-box mechanism (WBDL) based on dynamic library, ,which adopt MDS matrix. In this mechanism, different round-keys have been employed to implement encryption by randomly selecting look-up tables in each round of operations. According to the analysis, WBDL mechanism can resist differential attack, linear attack, BGE attack and side channel energy attack against SM4. After being calculated and tested, WBDL mechanism requires 466.914KB of memory to store the look-up tables, maximum differential probability(MDP) of each round is 2^−26, maximum linear probability(MLP) of each round is 2^−25.61, the encryption speed can reach to 0.273×10^−3 Gbps, and decryption speed can achieve 0.234×10^−3 Gbps. Our mechanism has better security and working efficiency, which can be used in mobile communication security and digital payment security.