Reputation systems offer web service consumers an effective solution for selecting web service providers who meet their Quality of Service (QoS) expectations. A reputation system computes the reputation of a provider as an aggregate of the feedback submitted by consumers. Truthful feedback is clearly a pre-requisite for accurate reputation scores. However, it has been observed that users of a reputation system often hesitate in providing truthful feedback, mainly due to the fear of reprisal from target entities.We present a privacy preserving reputation protocol that enables web service consumers to provide feedback about web service providers in a private and thus uninhibited manner.