Fault Injection to Reverse Engineer DES-Like Cryptosystems

International audienceSecurity is a key component for information technologies and communication and is mainly provided by cryptosystems. Although Kerckhoffs' principle enunciates that such cryptosystems should be secure even if their algorithms are public knowledge, private algorithms are still used. As the secrecy of such private algorithms ensures a large part of the security of the whole system, some attacks, called ``reverse-engineering'', aim at recovering these algorithms and/or details of their implementations. Among technics used to perform such attacks, a really efficient and powerful one, called “pertubation attacks”, consists in disrupting the circuit's behavior in order to alter the correct progress of the algorithm. Our work applies such technic to recover part of a crypto-algorithm based on the DES (for Data Encryption Standard) but which only differs from the values of its substitution boxes (or Sboxes).In the first part of the talk, the different technics of fault attacks will be shortly described. Then, our working hypothesis and our attack will be detailed. Next, the result obtained on simulated experiments will be presented. We’ll show that, with our approach, about two hundred of faulty executions of the algorithm enable to retrieve all the Sboxes. Compared with state of the art reverse engineering attacks based on faults, this number is reduced by a factor two