Building Trust for Lambda-Congenial Secret Groups

Establishing trust while preserving privacy is a challenging research problem. In this paper we introduce lambda -congenial secret groups which allow users to recognize trusted partners based on common attributes while preserving their anonymity and privacy. Such protocols are different from authentication protocols, since the latter are based on identities, while the former are based on attributes. Introducing attributes in trust establishment allows a greater flexibility but also brings up several issues. In this paper, we investigate the problem of building trust with attributes by presenting motivating examples, analyzing the security requirements and giving an informal definition. We also survey one of the most related techniques, namely private matching, and finally present solutions based on it

A NEW UNLINKABLE SECRET HANDSHAKES SCHEME BASED ON ZSS

Secret handshakes (SH) scheme is a key agreement protocol between two members of the same group. Under this scheme two members share a common key if and only if they both belong to the same group. If the protocol fails none of the parties involved get any idea about the group affiliation of the other. Moreover if the transcript of communication is available to a third party, she/he does not get any information about the group affiliation of communicating parties. The concept of SH was given by Balfanz in 2003 who also gave a practical SH scheme using pairing based cryptography. The protocol proposed by Balfanz uses one time credential to insure that handshake protocol performed by the same party cannot be linked. Xu and Yung proposed SH scheme that achieve unlinkability with reusable credentials. In this paper, a new unlinkable secret handshakes scheme is presented. Our scheme is constructed from the ZSS signature and inspired on an identity based authenticated key agreement protocol, proposed by McCullagh et al. In recently proposed work most of unlinkable secret handshake schemes have either design flaw or security flaw, we proved the security of proposed scheme by assuming the intractability of the bilinear inverse Diffie-Hellman and k-CAA problems

05411 Abstracts Collection -- Anonymous Communication and its Applications

From 09.10.05 to 14.10.05, the Dagstuhl Seminar 05411 ``Anonymous Communication and its Applications\u27\u27 was held in the International Conference and Research Center (IBFI), Schloss Dagstuhl. During the seminar, several participants presented their current research, and ongoing work and open problems were discussed. Abstracts of the presentations given during the seminar as well as abstracts of seminar results and ideas are put together in this paper. The first section describes the seminar topics and goals in general. Links to extended abstracts or full papers are provided, if available

PPAA: Peer-to-Peer Anonymous Authentication (Extended Version)

In the pursuit of authentication schemes that balance user privacy and accountability, numerous anonymous credential systems have been constructed. However, existing systems assume a client-server architecture in which only the clients, but not the servers, care about their privacy. In peer-to-peer (P2P) systems where both clients and servers are peer users with privacy concerns, no existing system correctly strikes that balance between privacy and accountability. In this paper, we provide this missing piece: a credential system in which peers are {\em pseudonymous} to one another (that is, two who interact more than once can recognize each other via pseudonyms) but are otherwise anonymous and unlinkable across different peers. Such a credential system finds applications in, e.g., Vehicular Ad-hoc Networks (VANets) and P2P networks. We formalize the security requirements of our proposed credential system, provide a construction for it, and prove the security of our construction. Our solution is efficient: its complexities are independent of the number of users in the system