Signature and Its Variants ?

We suggest several methods that may allow one to completely break cryptosystems implemented in a portable hardware device such as a smart card. These cryptanalytic methods work by exploring the hardware in such a way that the pseudo-random number generator embedded in the device behaves predictably, even for a very short period of time. While these attacking methods will be discussed by standing in the position of an attacker, our genuine intention is to serve as an alarm for users, developers and researchers in information security., Bellcore announced that D. Boneh, R. DeMillo (both of Bellcore) and R. Lipton (of Princeton University) have found that RSA signature generation/decryption key that is stored in a \tamper-proof" device such as a smart card may be extracted by an attacker who is in possession of the device 4]. The media release explains that the attack works by subjecting the tamper-proof device to certain types of physical stresses that would cause it to generate faulty computations. Technical details on the attack were later published in 7]. Prior to this, on 23 October 1996, six researchers from the National University of Singapore demonstrated in detail how an attacker may extract a secret RSA key stored in a \tamper-proof" device, again by subjecting the device to physical stresses 3]. The above attacks have been considered speciically for smart card implementations of public key cryptosystems (including decryption, signature, authentica-tion and identiication). A few weeks after Bellcore's media release, however, Bi-ham and Shamir announced, with suucient technical details, that practically all smart card implementations of private key cryptosystems (such as DES, IDEA, FEAL, : : :) may be broken within the same attack model where an attacker may introduce hardware faults into a \tamper-proof" device 6]. In less than two weeks' time, Biham and Shamir pushed their cryptanalysis further to show that hardware faults may allow one to break a smart card implementation of a private key cryptosystem whose algorithmic details are not public (for instance,