Paper 2005/034

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

Gene Tsudik and Shouhuai Xu


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.

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Publication info
Published elsewhere. PODC 2005 -- Brief Announcement
secret handshakesprivacy-preserving techniquesanonymitycredential systemsunobservabilitygroup key management
Contact author(s)
gts @ ics uci edu
2005-11-23: last of 3 revisions
2005-02-10: received
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      author = {Gene Tsudik and Shouhuai Xu},
      title = {Flexible Framework for Secret Handshakes (Multi-Party Anonymous and Un-observable Authentication)},
      howpublished = {Cryptology ePrint Archive, Paper 2005/034},
      year = {2005},
      note = {\url{}},
      url = {}
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