Security Evaluation of a Type of Table-Network Implementation of Block Ciphers

Abstract

Tamper-resistant software which implements a block cipher with a fixed embedded cryptographic key is important for securing embedded systems for digital rights management, access control, and other applications. The security of such software is measured by its ability to hide the embedded key against numerous known attacks. A class of methods for constructing tamper-resistant software by using a number of look-up tables is called a white-box implementation or table-network implementation. We developed a method of evaluating the security of table-network implementations of the Data Encryption Standard (DES). Link and Neumann proposed a table-network implementation of DES that is claimed to be resistant against all known attacks, which are effective for table-network implementations of DES proposed by Chow, Eisen, Johnson, and van Oorschot. In this paper, we point out the existence of a new attack, which allows efficient extraction of the hidden key in the Link-Newman table-network implementation of DES. Our result should contribute in completing the list of attacking methodologies and thus help the design of better tamper-resistant software.