Lanterna Rally

Author: Robert Patrick McEvoy

Publisher:

Published: 2008

Total Pages: 196

ISBN-13:

Cryptography plays a vital role in digital communications, working to ensure the privacy and integrity of the users and their data. However, in the last decade, attacks have emerged that target physical implementations of cryptographic algorithms. In particular, side-channel attacks are of concern. It is the task of the hardware engineer to ensure that implementations of these algorithms do not introduce weaknesses in the form of side-channel information, that could compromise the integrity of the cryptosystem. This thesis investigates side-channel attacks on FPGA implementations of cryptographic algorithms. The vulnerability of cryptographic hash functions to side-channel attacks is not usually considered in the literature. However, in protocols such as HMAC, hash functions are used to process secret key information, which can be recovered via a side-channel attack. Here, using a commercial FPGA, the vulnerability of the SHA-2 and Whirlpool hash functions to Differential Power Analysis (DPA) is proven. In response to such vulnerability, masking is a common DPA countermeasure used in academia and industry. New masking schemes are presented for both hash functions, and a novel method of converting from Boolean to arithmetic masks is developed. Secure logic styles ensure that the cryptographic device consumes a constant amount of power in each clock cycle, and represent a general countermeasure to side-channel attacks. The Double Wave Dynamic Differential Logic (DWDDL) secure logic style for FPGAs is examined, and leveraged to develop an alternative logic style, Isolated WDDL (IWDDL). Using laboratory experiments, a flaw in the DWDDL design flow is highlighted, and rectified. Another general side-channel attack countermeasure is proposed in the form of All-or-Nothing Transforms (AONTs). In this thesis, it is shown that All-or-Nothing Encryption and Decryption are inherently resistant to DPA attacks. This resistance is then further increased using a novel extension to the AONE protocol. Various AONT constructions are considered, and the performance of these schemes is analysed. The thesis concludes with a comparison of general side-channel attack countermeasures, to determine the most effective method of protecting cryptosystems against side-channel at-tacks. It is shown that a ryptosystem using the All-or-Nothing countermeasure can match the performance of (and, in certain cases, outperform) an unprotected implementation.