Title：A Designated Confirmer Signature Scheme from Bilinear Maps

　　　　  (Presentation will be given in Chinese)

Speaker：Guilin Wang（University of Birmingham, UK.）

Time：15:00-16:00 pm, Friday, December 18

Venue：Room 813, Level 8 Building #5

Abstract：

After the introduction of designated confirmer signatures (DCS) by Chaum in 1994, considerable researches have been made to build generic schemes from standard digital signatures or construct efficient concrete schemes. In DCS schemes, a signature cannot be verified without the help of either the signer or a semi-trusted third party, called the designated confirmer. If necessary, the confirmer can further convert a DCS into an ordinary signature that is publicly verifiable. However, most of the existing schemes are either inefficient or insecure. In this work, we propose a new designated confirmer signature scheme, and prove its security in the random oracle model under a modified version of definitions by Goldwasser and Waisbard. Our scheme is constructed from Boneh, Lynn and Shachams pairing based short signatures, and is efficient in both computational and communication aspects. In contrast to all previous solutions, our scheme supports unified verification. Namely, both the signer and the designated confirmer use the same protocol to confirm a valid DCS, and another same protocol to disavow an invalid signature. To the best of our knowledge, this is the first DCS scheme in which the signer is granted the disavowal ability.

Biography：

Guilin Wang is currently a lecturer in the School of Computer Science, University of Birmingham, UK. Before this, he was a research scientist in the Institute for Infocomm Research (I2R), Singapore (06/2002-09/2007), and an assistant professor in the Institute of Software, ChineseAcademy of Sciences (03/2001-05/2002). He received his PhD. degree in computer science from the Institute of Software, ChineseAcademy of Sciences, China, in March 2001. Dr. Wang has served as a program co-chair for two international security conferences (ICICS'08 and ISA'09), a program committee member for more than 30 international information security related conferences or workshops, and a reviewer for more than 20 international journals. Up to now, he has more than 50 technical publications in the areas of applied cryptography, information security, and electronic commerce. In particular, Dr. Wang is interested in the analysis and design of digital signatures and fair exchange protocols.