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Abstract

Processes for generating digital signatures for electronic messages. Modifying signature-generating algorithms, such as DSAs (Digital Signature Algorithms), in order to enable smart cards with reduced calculation and storage resources to produce digital signatures with a high degree of security in spite of their reduced resources. The signature-checking terminal sends a random number a and measures the time taken by the card to send back a signal s using this random number. If the time is greater than a given duration, the signature is rejected even if the check of its authenticity is positive. In addition, part of the signature (the part which does not use the secret card key but only the public algorithm parameters) is precalculated and stored in the card in the form of signature portions produced by a compression function such that they are short. Only the second part of the signature has to be calculated by the card. The calculations to be made are simple so that the card does not require extensive calculation and memory resources.

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First Claim