2001 | OriginalPaper | Buchkapitel
Security of Blind Discrete Log Signatures against Interactive Attacks
verfasst von : Claus Peter Schnorr
Erschienen in: Information and Communications Security
Verlag: Springer Berlin Heidelberg
Enthalten in: Professional Book Archive
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We present a novel parallel one-more signature forgery against blind Okamoto-Schnorr and blind Schnorr signatures in which an attacker interacts some l times with a legitimate signer and produces from these interactions l + 1 signatures. Security against the new attack requires that the following ROS-problem is intractable: find an overdetermined,s olvable system of linear equations modulo q withrandom inhomogenities (right sides).There is an inherent weakness in the security result of Pointcheval and Stern. Theorem 26[PS00] does not cover attacks with 4 parallel interactions for elliptic curves of order 2200. That would require the intractability of the ROS-problem, a plausible but novel complexity assumption. Conversely, assuming the intractability of the ROS-problem, we show that Schnorr signatures are secure in the random oracle and generic group model against the one-more signature forgery.