Time-selective convertible undeniable signatures with short conversion receipts |
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Authors: | Fabien Laguillaumie |
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Affiliation: | a GREYC, Université de Caen, Campus 2, Boulevard du Maréchal Juin, BP 5186, 14032 Caen Cedex, France b École normale supérieure - C.N.R.S. - I.N.R.I.A., Département d’informatique, 45 rue d’Ulm, 75230 Paris Cedex 05, France |
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Abstract: | Undeniable signatures were introduced in 1989 by Chaum and van Antwerpen to limit the self-authenticating property of digital signatures. An extended concept - the convertible undeniable signatures - proposed by Boyar, Chaum, Damgård and Pedersen in 1991, allows the signer to convert undeniable signatures to ordinary digital signatures.In this article, we present a new efficient convertible undeniable signature scheme based on bilinear maps. Its unforgeability is tightly related, in the random oracle model, to the computational Diffie-Hellman problem and its anonymity to a non-standard decisional assumption. The advantages of our scheme are the short length of the signatures, the low computational cost of the signature and the receipt generation. Moreover, a variant of our scheme permits the signer to universally convert signatures pertaining only to a specific time period. We formalize this new notion as the time-selective conversion. We also improve our original scheme from CT-RSA’05 by reducing the length of the generated receipts: their size is now logarithmic in the number of time periods. |
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Keywords: | Convertible undeniable signatures Bilinear maps Anonymity Exact security Time-selective conversion |
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