Patent ID: 7240198

Claim:
A method for preserving the integrity of a negotiation conducted via a network, and using clients and/or servers, among a plurality of parties each of whom is making a private input during the negotiation and wherein a trusted entity acting as a center computers and outputs a value F of these inputs constituting the output of the negotiation comprising the steps of: a) providing an architecture which includes a center A, and a plurality of participants B.sub.1, B.sub.2, . . . , B.sub.n, to engage in a negotiation during which all communications originating with a participant B.sub.i and transmitted to center A are exclusive; b) secretly generating an input x.sub.i by each participant B.sub.i; c) publishing by the center A to each participant a commitment to K combinatorial circuits that compute F, where K is a security parameter; d) transmitting by each participant B.sub.i to the center A a commitment c.sub.i to the value of B.sub.i's input x.sub.i, where c.sub.i is an encryption of x.sub.i; e) responsive to receipt of the commitments of the participants, publishing by the center A to the participants the commitments received; f) providing to each participant B.sub.i part of the K combinatorial circuits that the center A committed to, and requesting center A to open them, whereupon each participant B.sub.i can verify that the part of the circuits opened to participant B.sub.i computes a value F; g) transmitting by each participant B.sub.i to center A its input x.sub.i and decryption data to enable center A to verify that x.sub.i corresponds to the transmitted commitment c.sub.i; h) computing by center A a value of F based on the inputs x.sub.i it received by using a part of the K combinatorial circuits not disclosed to the participants, and publishing the computed value of F to the participants; and i) transmitting to all participants a proof that the computed value of F was computed correctly, which proof can be verified by each participant using the published commitments while preventing a coalition of any one subset of participants from learning (i) anything which cannot be computed just from the output of the K combinatorial circuits and from their own inputs, and (ii) information about the inputs of the other users.