Patent ID: 8498415

Claim:
A method for preserving privacy of a reputation inquiry in a peer-to-peer computer networking communication environment with an inquiry handler, a response handler, a plurality of parties including at least one responder, an inquirer, an inquiry target, wherein the responder has a rating score that rates the inquiry target, the method comprising the steps of: generating an inquiry vector about the inquiry target, wherein the inquiry vector has a plurality of elements and the generating step is performed by the inquirer; applying homomorphic encryption, by the inquirer, to each element of the inquiry vector and specifying a corresponding encryption key, thereby producing an encrypted inquiry, wherein the encryption key is known by the inquirer and is not known by the inquiry handler, the response handler, the inquiry target or the responder, the inquiry handler and the response handler being separate entities, thereby achieving a separation of duty between the inquiry handler and the response handler; sending the encrypted inquiry, across a computer network, to the inquiry handler; broadcasting the encrypted inquiry to the responder, wherein the broadcasting step is performed by the inquiry handler, identifying the response handler to the responder such that each responder can send a response to the response handler, the step of identifying the response handler being performed by the inquiry handler; responding by raising each element of the encrypted inquiry vector by a power equal to the rating score, thereby generating a response to the inquiry, wherein the raising step is performed by the responder; transmitting the responses, across a computer network, from the responder to the response handler; producing a summary response, wherein the step of producing is performed by the response handler; sending the summary response from the response handler to the inquirer; and decrypting the encrypted summary response using a decryption key; wherein the step of responding responds by constructing a rating vector make 13 RV(R Pi ,i)=T i ×R Pi wherein R Pi is a vector storing a rating score for each of the parties P i , where T i is a transformation matrix of size n 2 ×n for mapping R Pi of size n×1 to rating vector V Pi of size n 2 ×1 with zero padding, and T i T =[Z n×n(i−1) I n×n Z n×n(n−i) ]is composed of a zero matrix of size n×n(i−1), an identity matrix of size n×n, and another zero matrix of size n×n(n−i), and then applying a response function make_Response(V Pi , IV Pk )=Π j=1 n×n (k mj ) vj , where vj is j th entry in the V Pi , and k mj is the j th entry in IV Pk , to raise each element of the encrypted inquiry vector by the power equal to the rating score.