Storing Classified Files

Authors: Shai Halevi and Erez Petrank.

Note: Similar results were published by Gerald C. Chick and Stafford E. Tavares, "Flexible access control with master keys". Advances in Cryptology: CRYPTO '89, LNCS, vol. 435, Springer-Verlag, 1990. Pages 316-322.

Abstract: We study a natural problem in secure systems, namely - storing classified files on-line. A system of classified files contains a set of files (or documents), a set of users, and an authorization structure which defines the subset of files each user is authorized to see. We want a user in the system to be able to see every file in her ``authorized list'' but not any other file.

We present definitions of secure classified file systems and discuss various aspects of such systems, such as static versus dynamic models, resilience, the role of a central trusted entity, etc. We also present a highly space-efficient implementation for a secure system which is based on RSA.

Availability: Paper available as Gzipped PostScript (69 Kbyte).

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