Abstract
With blackmailing we mean a situation where after a signature has been verified, the conviction of its correctness can be either kept to the verifier or, at his sole discretion, be shared with some predetermined set of cooperating co-verifiers. We show how a weakness in the protocol for undeniable signatures allows blackmailing of a signer of a undeniable signature, or several verifiers simultaneously to verify several signatures. Also, we discuss how multiple verifiers can be convinced about the correctness of a signature in similar protocols, like Designated Confirmer Signatures, although no blackmailing attack is found for here.
The author was supported by Claes Adelskjölds fund, Gustav Sigurd Magnussons fund and von Beskows fund, The Royal Swedish Academy of Sciences
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References
D. Chaum, H. van Antwerpen, “Undeniable Signatures,” Crypto '89, pp. 212–216
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© 1995 Springer-Verlag Berlin Heidelberg
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Jakobsson, M. (1995). Blackmailing using undeniable signatures. In: De Santis, A. (eds) Advances in Cryptology — EUROCRYPT'94. EUROCRYPT 1994. Lecture Notes in Computer Science, vol 950. Springer, Berlin, Heidelberg. https://doi.org/10.1007/BFb0053457
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DOI: https://doi.org/10.1007/BFb0053457
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