A white-box AES-like implementation based on key-dependent substitution-linear transformations

Abstract

It is becoming increasingly common to deploy cryptographic algorithms within software applications which are executed in untrusted environments owned and controlled by a possibly malicious party. White-box cryptography aims to protect the secret key in such an environment. Chow et al. developed a white-box AES implementation in 2002 by hiding secret keys into lookup tables. Afterwards, some improvements were proposed. However, all the published schemes have been shown to be insecure. AES was originally designed without consideration of execution in a white-box attack context. Because of the fixed confusion and diffusion operations, it is easy to break AES’s white-box version. In this paper, we propose an AES-like cipher by replacing AES’s S-boxes and MixColumn matrices with key-dependent components while keeping their good cryptographic properties. We show that the white-box implementation of our AES-like cipher can resist current known attacks.