Title: An Observation about Variants of the Diffie-Hellman Assumption
Start Time: 12/05/2008 - 11:00
End Time: 12/05/2008 - 12:00
Location: ICT 618B
Speaker: Yacov Yacobi, Microsoft Research
Abstract:
Many researchers looked at the Boneh-Boyen signature scheme for Anonymous Credentials applications. In credential systems, usually we present credentials as vectors. One can easily sign a vector using any ordinary digital signature scheme, by first hashing the vector into a relatively short message and then signing it. However, credential systems are very intricate, and have many additional requirements. The ability to sign vectors without destroying the algebraic structure may
help accomplish some of those difficult requirements (but may also open the doors to new attacks, so one must be careful). Our complexity theoretic result may be of interest in such cases. We generalize the Strong Boneh-Boyen (SBB) signature scheme to sign vectors (GSBB). There is a trivial worst-case polynomial time reduction from SBB to GSBB. We show that if an average case reduction exists then the Strong Diffie- Hellman (SDH) and the Computational Diffie-Hellman (CDH) have the same worst-case complexity.
Biography:
Yacov Yacobi is a Principal Researcher at Microsoft-Research.
Founder and head of the Cryptography & Anti-Piracy research group in Microsoft Research (from 1997 to October 2007). Current personal research includes cryptography, economic analysis of anti-piracy systems, electronic payment systems, and the quantification of trust.
Member of the editorial boards of the Journal of Computer Security, and of ACM Wireless Networks. Member of the CISaC Technical Advisory Panel. Guest co-editor of two issues on security of IEEE Wireless Communications (and was a member of the editorial board for a decade).
Prior to joining Microsoft in 1995 was a Senior-Researcher at the Applied Research Division of Bellcore (now Telcordia). Doctor of Science in Electrical Engineering from the Technion, Israel Institute of Technology.