Hidden Credentials are a new way of managing access to resources governed by attribute-based access control policies. They are especially useful in situations where requests for service, credentials, access policies and resources are extremely sensitive. We show how transactions which depend on fulfillment of policies described by monotonic boolean formulae can take place in a single round of messages. We further show how credentials that are never revealed can be used to retrieve sensitive resources. Hidden Credentials let Alice encrypt a message in such a way that Bob can only decrypt if he has the right credentials. That is, his credentials are the decryption key. Using ideas from identity-based cryptosystems, Alice constructs the public keys for Bob's credentials based solely on credential names, without help from any outside party and regardless of whether those credentials have actually been issued to him. We also provide an implemenation of our Hidden Credential system which can be found here.
J. Holt, R. Bradshaw, K. E. Seamons, and H. Orman. Hidden Credentials. 2nd ACM Workshop on Privacy in the Electronic Society, Washington, DC, October 2003.
R. Bradshaw, J. Holt, and K. E. Seamons. Concealing Complex Policies with Hidden Credentials. Eleventh ACM Conference on Computer and Communications Security, Washington, DC, October 2004.
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