## Cryptology ePrint Archive: Report 2005/034

Flexible Framework for Secret Handshakes (Multi-Party Anonymous and Un-observable Authentication)

Gene Tsudik and Shouhuai Xu

Abstract: In the society increasingly concerned with the erosion of privacy, privacy-preserving techniques are becoming very important. This motivates research in cryptographic techniques offering built-in privacy.

A secret handshake is a protocol whereby participants establish a secure, anonymous and unobservable communication channel only if they are members of the same group. This type of private" authentication is a valuable tool in the arsenal of privacy-preserving cryptographic techniques. Prior research focused on 2-party secret handshakes with one-time credentials.

This paper breaks new ground on two accounts: (1) it shows how to obtain secure and efficient secret handshakes with reusable credentials, and (2) it represents the first treatment of group (or {\em multi-party}) secret handshakes, thus providing a natural extension to the secret handshake technology. An interesting new issue encountered in multi-party secret handshakes is the need to ensure that all parties are indeed distinct. (This is a real challenge since the parties cannot expose their identities.) We tackle this and other challenging issues in constructing GCD -- a flexible framework for secret handshakes.

The proposed framework lends itself to many practical instantiations and offers several novel and appealing features such as self-distinction and strong anonymity with reusable credentials. In addition to describing the motivation and step-by-step construction of the framework, this paper provides a thorough security analysis and illustrates two concrete framework instantiations.

Category / Keywords: secret handshakes, privacy-preserving techniques, anonymity, credential systems, unobservability, group key management

Publication Info: PODC 2005 -- Brief Announcement

Date: received 8 Feb 2005, last revised 23 Nov 2005

Contact author: gts at ics uci edu

Available format(s): PDF | BibTeX Citation

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