In this paper we analyse the Digital Signature Algorithm (DSA) and its immunity to the fault cryptanalysis that takes advantage of errors inducted into the private key a. The focus of our attention is on the DSA scheme as it is a widely adopted by the research community, it is known to be vulnerable to this type of attack, but neither sound nor effective modifications to improve its immunity have been proposed. In our paper we consider a new way of implementing the DSA that enhances its immunity in the presence of faults. Our proposal ensures that inducting errors into the private key has no benefits since the attacker cannot deduce any information about the private key given erroneous signatures. The overhead of our proposal is similar to the overhead of obvious countermeasure based on signature verification. However, our modification generates fewer security issues.
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