Abstract: A server system receives requests from client systems and sends responses back to the client systems. For a subset of the requests, in addition to responding to a request from a client system, the method includes creating a cryptographic object at the server system. The cryptographic object is used to cryptographically protect information related to the request, and the cryptographically protected information associated with the cryptographic object is stored at the server system. The server system then sends the cryptographic object to the client system, and in conjunction with sending the cryptographic object to the client system, irreversibly modifies the cryptographic object on the server system. For example, in some embodiments the cryptographic object includes an cryptographic key, and the server system deletes or truncates the only instances of the cryptographic object on the server system when the server system finishes responding to the request from the client system.