Jiangtao Li and Ninghui Li

CERIAS TR 2004-11

conference

SUPERCEDED BY CERIAS TR 2005-26 We propose Oblivious Attribute Certificates (OACerts), an attribute certificate scheme in which a certificate holder can select which attributes to use and how to use them. In particular, a user can use attribute values stored in an OACert obliviously, \ie, the user obtains a service if and only if the attribute values satisfy the policy of the service provider, yet the service provider learns nothing about these attribute values. To build OACerts, we propose a new cryptographic primitive called Oblivious Commitment Based Envelope (OCBE). In an OCBE scheme, Bob has an attribute value committed to Alice and Alice runs a protocol with Bob to send an envelope (encrypted message) to Bob such that: (1) Bob can open the envelope if and only if his committed attribute value satisfies a predicate chosen by Alice. (2) Alice learns nothing about Bob's attribute value. We develop provably secure and efficient OCBE protocols for the Pedersen commitment scheme and predicates such as $=,\ge,\le,>,<,\ne$ as well as logical combinations of them.

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2004 – 10 – 01

Purdue University

Li

CERIAS and Department of Computer Sciences

2004-10-01

OACerts: Oblivious Attribute Certificates