Security

Fault Attacks on RSA Signatures With Partially Unknown Messages

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Executive Summary

Fault attacks exploit hardware malfunctions to recover secrets from embedded electronic devices. In the late 90's, Boneh, DeMillo and Lipton introduced fault-based attacks on CRT-RSA. These attacks factor the signer's modulus when the message padding function is deterministic. However, the attack does not apply when the message is partially unknown, for example when messages contain some randomness which is recovered only when verifying a correct signature. In this paper the authors successfully extends RSA fault attacks to a large class of partially known message configurations. The new attacks rely on Coppersmith's algorithm for finding small roots of multivariate polynomial equations.

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