Attacking block ciphers

Abstract

Differential Fault Analysis (DFA) was one of the earliest techniques invented to attack block ciphers by provoking a computational error. In the basic DFA scenario the adversary obtains a pair of ciphertexts both of which encrypt the same plaintext. One of these ciphertexts is the correct result while the other is an erroneous one resulting from a faulty computation. Though applications of DFA to DES and AES have proven to be quite effective, other techniques have also been invented which can threaten block ciphers in different ways. This chapter presents some of these fault analysis methods, including Collision Fault Analysis (CFA) and its close variant Ineffective Fault Analysis (IFA). These methods depart from DFA by the fault model they rely on, by their ability to defeat classical countermeasures against DFA or DPA, or by their application to specific implementations.