Using Tweaks To Design Fault Resistant Ciphers (Full Version)

Abstract

Side channel analysis and active fault analysis are now major threats to even mathematically robust cryptographic algorithms that are otherwise resistant to classical cryptanalysis. It is necessary to design suitable countermeasures to protect cryptographic primitives against such attacks. This paper focuses on designing encryption schemes that are innately secure against fault analysis. The paper formally proves that one such design strategy namely the use of key-dependent S-Boxes, is only partially secure against DFA. The paper then examines the fault tolerance of encryption schemes that use a key-independent secret tweak value for randomization. In particular, the paper focuses on a linear tweak based and a non-linear tweak based version of a recently proposed block cipher DRECON. The paper demonstrates that while both versions are secure against classical DFA, the non-linear tweak based version provides greater fault coverage against stronger fault models. This fact, together with the DPA resistance provided by the use of variable S-Boxes, makes DRECON a strong candidate for the design of secure cryptographic primitives. All claims have been validated by experimental results on a SASEBO GII platform.