Flexible multi-client functional encryption for set intersection.

A multi-client functional encryption (MCFE) scheme [Goldwasser-Gordon-Goyal 2014] for set intersection is a cryptographic primitive that enables an evaluator to learn the intersection from all sets of a predetermined number of clients, without need to learn the plaintext set of each individual client. Using these schemes, it is impossible to compute the set intersections from arbitrary subsets of clients, and thus, this constraint limits the range of its applications. To provide such a possibility, we redefine the syntax and security notions of MCFE schemes, and introduce flexible multi-client functional encryption (FMCFE) schemes. We extend the aIND security of MCFE schemes to aIND security of FMCFE schemes in a straightforward way. For a universal set with polynomial size in security parameter, we propose an FMCFE construction for achieving aIND security. Our construction computes set intersection for n clients that each holds a set with m elements, in time O(nm). We also prove the security of our construction under DDH1 that it is a variant of the symmetric external Diffie-Hellman (SXDH) assumption.

Optimal Wastewater Loading under Conflicting Goals and Technology Limitations in a Riverine System.

This paper investigates a novel simulation-optimization (S-O) framework for identifying optimal treatment levels and treatment processes for multiple wastewater dischargers to rivers. A commonly used water quality simulation model, Qual2K, was linked to a Genetic Algorithm optimization model for exploration of relevant fuzzy objective-function formulations for addressing imprecision and conflicting goals of pollution control agencies and various dischargers. Results showed a dynamic flow dependence of optimal wastewater loading with good convergence to near global optimum. Explicit considerations of real-world technological limitations, which were developed here in a new S-O framework, led to better compromise solutions between conflicting goals than those identified within traditional S-O frameworks. The newly developed framework, in addition to being more technologically realistic, is also less complicated and converges on solutions more rapidly than traditional frameworks. This technique marks a significant step forward for development of holistic, riverscape-based approaches that balance the conflicting needs of the stakeholders.