On the weight enumerator of product codes

AbstractThe number of words of weight w in the product code of linear codes with minimum distances dr and dc is expressed in the number of low weight words of the constituent codes, provided that w < drdc + max(dr, dc). By examples it is shown that, in general, the full weight enumerator of a product code is not completely determined by the weight enumerator of its constituent codes

Protection of software algorithms executed on secure modules

Loop structures in software code may reveal essential information about implemented algorithms and their parameters, even if the observer has no knowledge about which instructions are executed. Regular patterns can for instance be observed in power consumption, instruction fetches in external memory, or radiated EM energy. This paper addresses the use of dummy operations to obscure the details of the algorithm executed by the processor. We show that for a particular class of dummy insertion strategies, a Viterbi decoder can fairly reliably distinguish dummy fetches from real instruction fetches. In the second part of this paper, we study strategies to choose dummy fetches from a more general model. For certain situations, the optimum protection strategy appears to be deterministic (as opposed to random). Moreover, we show that in such a case, it is fundamentally not possible to enhance the security of the implementation by keeping the strategy for generating dummy fetches secret to the attacker. Author Keywords: Software protection; Secure processor; Viterbi decoder; Dummy instruction

New binary linear block codes

Using some known techniques, several new binary linear codes are constructed, i.e., codes with a greater minimum distance than any previously known binary code of the same length and dimension [8]. A detailed description of one of the constructions is given

A sharpening of the Johnson bound for binary linear codes and the nonexistence of linear codes with preparata parameters

We show fort>3 the nonexistence of binary [2 t –2, 2 t –2t–1, 5] codes