Cryptology ePrint Archive: Report 2004/211

Scalable, Server-Passive, User-Anonymous Timed Release Public Key Encryption from Bilinear Pairing

Ian F. Blake and Aldar C-F. Chan

Abstract: We consider the problem of sending messages into the future, commonly known as timed release cryptography. Existing schemes for this task either solve the relative time problem with uncontrollable, coarse-grained release time (time-lock puzzle approach) or do not provide anonymity to sender and/or receiver and are not scalable (server-based approach). Using a bilinear paring on any Gap Diffie-Hellman group, we solve this problem by giving a scalable, server-passive and user-anonymous timed release public-key encryption scheme which allows precise absolute release time specifications. Unlike the existing server-based schemes, the trusted time server in our scheme is completely passive --- no interaction between it and the sender or receiver is needed; it is even not aware of the existence of a user, thus assuring the anonymity of both the sender and receiver of a message and the privacy of the message. Besides, our scheme also has a number of desirable properties including self-authenticated time-bound key updates, a single form of update for all receivers, simple public-key renewal and key insulation, making it a scalable and appealing solution.

Category / Keywords: timed release encryption, bilinear pairing, identity-based encryption, anonymity

Publication Info: -

Date: received 25 Aug 2004, last revised 9 Sep 2004

Contact author: aldar at comm utoronto ca

Available format(s): Postscript (PS) | Compressed Postscript (PS.GZ) | PDF | BibTeX Citation

Version: 20040909:132145 (All versions of this report)

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