Abstract. Motivated by the need to outsource file storage to untrusted clouds while still permitting limited use of that data by third parties, we present practical protocols by which a client (the third-party) can evaluate a deterministic finite automaton (DFA) on an encrypted file stored at a server (the cloud), once authorized to do so by the file owner. Our protocols provably protect the privacy of the DFA and the file contents from a malicious server and the privacy of the file contents (except for the result of the evaluation) from an honest-but-curious client (and, heuristically, from a malicious client). We further present simple techniques to detect client or server misbehavior.
The protocol we design here directly builds on a previous protocol REF that enables a client to evaluate a deterministic finite automaton (DFA) on the plaintext of an encrypted file hosted by a server provided that the client has been given permission to do so by the data owner.
Third-Party Private DFA Evaluation on Encrypted Files in the Cloud
ESORICS
Computer Science