pRate: Anonymous Star Rating with Rating Secrecy

We introduce pRate, a novel reputation management scheme with strong security and privacy guarantees for the users and their reputation scores. The reputation scores are computed based on the (aggregated) number(s) of stars that users receive from their raters. pRate allows users to advertise privacy-friendly statements about their reputation when searching for potential transaction partners. Ratings can only be submitted by partners who have been initially authorised by the ratee and issued a rating token. The scheme is managed by a possibly untrusted reputation manager who can register users and assist ratees in updating their reputation scores, yet without learning these scores. In addition to ensuring the secrecy of the ratings, a distinctive feature of pRate over prior proposals, is that it hides the identities of raters and ratees from each other during the transaction and rating stages. The scheme is built from a number of efficient cryptographic primitives; its security is formally modeled and proven to hold under widely used assumptions on bilinear groups.