We present the first non-trivial constructions of (non-interactive) forward-secure public-key encryption schemes. Our main construction achieves security against chosen-plaintext attacks under the decisional bilinear Diffie-Hellman assumption in the standard model. This scheme is practical, and all parameters grow at most logarithmically with the total number of time periods. We also give a slightly more efficient scheme in the random oracle model. Both our schemes can be extended to achieve security against chosen-ciphertext attacks and to support an unbounded number of time periods.
Toward our goal, we introduce the notion of \emph{binary tree encryption} and show how to construct a binary tree encryption scheme in the standard model. This new primitive may be of independent interest. In particular, we use it to construct the first known example of a (hierarchical) identity-based encryption scheme that is secure in the standard model. (Here, however, the notion of security we achieve is slightly weaker than what is achieved in some previous constructions in the random oracle model.)
Category / Keywords: public-key cryptography / forward security, BDH assumption Publication Info: Eurocrypt 2003 Date: received 1 May 2003, last revised 23 Dec 2003 Contact author: jkatz at cs umd edu Available format(s): Postscript (PS) | Compressed Postscript (PS.GZ) | PDF | BibTeX Citation Note: This paper supersedes a previous version which appears as ePrint archive report 2002/060. Version: 20031223:175208 (All versions of this report) Short URL: ia.cr/2003/083