Hidden Access Control Policies with Hidden Credentials

Jan 19, 2005

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Abstract

In an open environment such as the Internet, the decision to
collaborate with a stranger (e.g., by granting access to a
resource) is often based on the characteristics (rather than the
identity) of the requester, via digital credentials: Access is
granted if Alice's credentials satisfy Bob's access policy. The
literature contains many scenarios in which it is desirable to
carry out such trust negotiations in a privacy-preserving manner,
i.e., so as minimize the disclosure of credentials and/or of
access policies. Elegant solutions were proposed for achieving
various degrees of privacy-preservation through minimal
disclosure. We present efficient protocols that
protect both sensitive credentials and sensitive policies. That is,
Alice gets the resource only if she satisfies the policy, Bob
does not learn anything about Alice's credentials (not even whether
Alice gained access or not), and Alice learns neither Bob's policy
structure nor which credentials caused her to gain access.