Computing multi-party trust privately: In O(n) time units sending one (possibly large) message at a time

Schemes for multi-party trust computation are presented. The schemes do not make use of a Trusted Authority. The schemes are more efficient than previous schemes by the number of messages exchanged which is proportional to the number of participants rather than to a quadratic number of the participants. We note that in our schemes the length of each message may be larger than the message length of previous schemes. The calculation of a trust, in a specific user by a group of community members, starts upon a request of an initiating user. The trust computation is provided in a completely distributed manner, while each user calculates its trust value privately. Given a community C and its members (users) U₁, ..., U_n, we present computationally secure schemes for trust computation. The first Accumulated Protocol AP computes the average trust in a specific user U_t upon the trust evaluation request initiated by a user U_n. The exact trust values of each queried user are not disclosed to U_n. The next Weighted Accumulated protocol WAP generates the average weighted trust in a specific user U_t taking into consideration the unrevealed trust that U_n has in each user participating in the trust process evaluation. We extend our schemes to the case when the initiating user U_n can be compromised by the adversary, and we introduce the Multiple Private Keys M P K P and the Multiple Private Keys Weighted M P W P protocols for computing average unweighted and weighted trust, respectively. The computation of all our algorithms requires the transmission of O(n) (possibly large) messages.