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D. Deuber, M. Maffei, G. Malavolta, M. Rabkin, D. Schröder, M. Simkin:
"Functional Credentials";
in: "Proceedings on Privacy Enhancing Technologies", Volume 2018: Issue 2; issued by: De Gruyter Open; Walter de Gruyter GmbH, Berlin, 2018, 64 - 84.

A functional credential allows a user to anony-
mously prove possession of a set of attributes that fulfills
a certain policy. The policies are arbitrary polynomially
computable predicates that are evaluated over arbitrary
attributes. The key feature of this primitive is the dele-
gation of verification to third parties, called designated
verifiers. The delegation protects the
privacy of the pol-
icy
: A designated verifier can verify that a user satisfies a
certain policy without learning anything about the pol-
icy itself. We illustrate the usefulness of this property
in different applications, including outsourced databases
with access control. We present a new framework to
construct functional credentials that does not require
(non-interactive) zero-knowledge proofs. This is impor-
tant in settings where the statements are complex and
thus the resulting zero-knowledge proofs are not effi-
cient. Our construction is based on any predicate en-
cryption scheme and the security relies on standard as-
sumptions. A complexity analysis and an experimental
evaluation confirm the practicality of our approach.

http://dx.doi.org/10.1515/popets-2018-001

https://publik.tuwien.ac.at/files/publik_270460.pdf