Time-Selective Convertible Undeniable Signatures with Short Conversion Receipts

Fabien Laguillaumie (1) , Damien Vergnaud (2)

1 Equipe AMACC - Laboratoire GREYC - UMR6072
2 CASCADE - Construction and Analysis of Systems for Confidentiality and Authenticity of Data and Entities

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.

Mots clés: Convertible undeniable signatures; bilinear maps; anonymity; exact security; time- selective conversion

Domaines: Informatique [cs]; Cryptographie et sécurité [cs.CR]

Fabien Laguillaumie, Damien Vergnaud. Time-Selective Convertible Undeniable Signatures with Short Conversion Receipts. Information Sciences, 2010, pp.2458-2475. ⟨hal-01087046⟩