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International audienceThis paper describes the forensic analysis of what the authors believe to be the most sophisticated smart card fraud encountered to date. In 2010, Murdoch et al. (IEEE Symposium on Security and Privacy, pp 433–446, 2010) described a man-in-the-middle attack against EMV cards. Murdoch et al. (IEEE Symposium on Security and Privacy, pp 433–446, 2010) demonstrated the attack using a general purpose FPGA board, noting that “miniaturization is mostly a mechanical challenge, and well within the expertise of criminal gangs”. This indeed happened in 2011, when about 40 sophisticated card forgeries surfaced in the field. These forgeries are remarkable in that they embed two chips wired top-to-tail. The first chip is clipped from a genuine stolen card. The second chip plays the role of the man-in-the-middle and communicates directly with the point of sale terminal. The entire assembly is embedded in the plastic body of yet another stolen card. The forensic analysis relied on X-ray chip imaging, side-channel analysis, protocol analysis, and microscopic optical inspections

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Abstract. In two-party computation, achieving both fairness and guaranteed output delivery is well known to be impossible. Despite this limitation, many approaches provide solutions of practical interest by weakening somewhat the fairness requirement. Such approaches fall roughly in three categories: "gradual release" schemes assume that the aggrieved party can eventually reconstruct the missing information; "optimistic schemes" assume a trusted third party arbitrator that can restore fairness in case of litigation; and "concurrent" or "legally fair" schemes in which a breach of fairness is compensated by the aggrieved party having a digitally signed cheque from the other party (called the keystone). In this paper we describe and analyse a new contract signing paradigm that doesn't require keystones to achieve legal fairness, and give a concrete construction based on Schnorr signatures which is compatible with standard Schnorr signatures and provably secure.

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