Secure protocols for accountable warrant execution

We describe cryptographic protocols for secure execution of warrants or legal orders authorizing access to data held by private parties. Using cryptography enables a better combination of security, privacy, and accountability properties than would otherwise be possible. We describe a series of protocols, based on different assumptions about trust and technical sophistication of the parties, and making use of wellstudied cryptographic tools. We report benchmark results from our prototype implementation of the tools involved in one such protocol, and show that the protocol’s entire computational cost is easily feasible even for very large data sets, such as “cloud” software service or telecommunications databases comprising billions of records.