Method and system for multi-authority controlled functional encryption

A method for performing an encryption scheme in a system having a plurality of servers, the method comprising:

• receiving, by a first server of the plurality of servers, a request from a client to compute a function on a data point, the data point being encrypted as a ciphertext and the request including a request token generated by the client based on the ciphertext and the function;
• and
• granting, by the first server, the request to compute the function on the data point by sending a function evaluation key to the client, wherein the function evaluation key is generated by the first server based on the request token and a master secret key associated with the first server, wherein the master secret key is based on a share of a secret key under a linearly-homomorphic encryption scheme and another secret key under an adaptive chosen ciphertext attack encryption scheme,
• wherein the function evaluation key is one of a plurality of function evaluation keys, each function evaluation key in the plurality of function evaluation keys corresponding to one of the plurality of servers participating in a distributed decryption protocol, and the plurality of function evaluation keys enable the client to generate a result of computing the function on the data point.