Mix-nets are used in e-voting schemes and other applications that require anonymity. Shuffles of homomorphic encryptions are often used in the construction of mix-nets. A shuffle permutes and re-encrypts a set of ciphertexts, but as the plaintexts are encrypted it is not possible to verify directly whether the shuffle operation was done correctly or not. Therefore, to prove the correctness of a shuffle it is often necessary to use zero-knowledge arguments. We propose an honest verifier zero-knowledge argument for the correctness of a shuffle of homomorphic encryptions. The suggested argument has sublinear communication complexity that is much smaller than the size of the shuffle itself. In addition the suggested argument matches the lowest computation cost for the verifier compared to previous work and also has an efficient prover. As a result our scheme is significantly more efficient than previous zero-knowledge schemes in literature. We give performance measures from an implementation where the correctness of a shuffle of 100,000 ElGamal ciphertexts is proved and verified in around 2 minutes.

Abstract. Verification of a polynomial's evaluation in a secret committed value plays a role in cryptographic applications such as non-membership or membership proofs. We construct a novel special honest verifier zero-knowledge argument for correct polynomial evaluation. The argument has logarithmic communication cost in the degree of the polynomial, which is a significant improvement over the state of the art with cubic root complexity at best. The argument is relatively efficient to generate and very fast to verify compared to previous work. The argument has a simple public-coin 3-move structure and only relies on the discrete logarithm assumption.The polynomial evaluation argument can be used as a building block to construct zero-knowledge membership and non-membership arguments with communication that is logarithmic in the size of the blacklist. Non-membership proofs can be used to design anonymous blacklisting schemes allowing online services to block misbehaving users without learning the identity of the user. They also allow the blocking of single users of anonymization networks without blocking the whole network.

The Ombudsman Office at a large academic medical center created a standardized approach to manage and measure unsolicited patient complaints, including methods to identify longitudinal improvements, accounting for volume variances, as well as incident severity to prioritize response needs. Data on patient complaints and grievances are collected and categorized by type of issue, unit location, severity, and individual employee involved. In addition to granular data, results are collated into meaningful monthly leadership reports to identify opportunities for improvement. An overall benchmark for improvement is also applied based on the number of complaints and grievances received for every 1000 patient encounters. Results are utilized in conjunction with satisfaction survey results to drive patient experience strategies. By applying benchmarks to patient grievances, targets can be created based on historical performance. The utilization of grievance and complaint benchmarking helps prioritize resources to improve patient experiences.