Traditionally, research focusing on the design of routing and staffing policies for service systems has modeled servers as having fixed (possibly heterogeneous) service rates. However, service systems are generally staffed by people. Furthermore, people respond to workload incentives; that is, how hard a person works can depend both on how much work there is, and how the work is divided between the people responsible for it. In a service system, the routing and staffing policies control such workload incentives; and so the rate servers work will be impacted by these policies. This observation has consequences when modeling service system performance, and our objective in this paper is to investigate those consequences.

We consider the problem of designing distribution rules to share `welfare' (cost or revenue) among individually strategic agents. There are many known distribution rules that guarantee the existence of a (pure) Nash equilibrium in this setting, e.g., the Shapley value and its weighted variants; however, a characterization of the space of distribution rules that guarantee the existence of a Nash equilibrium is unknown. Our work provides an exact characterization of this space for a specific class of scalable and separable games, which includes a variety of applications such as facility location, routing, network formation, and coverage games. Given arbitrary local welfare functions $W$, we prove that a distribution rule guarantees equilibrium existence for all games (i.e., all possible sets of resources, agent action sets, etc.) if and only if it is equivalent to a generalized weighted Shapley value on some `ground' welfare functions $W$, which can be distinct from W. However, if budget-balance is required in addition to the existence of a Nash equilibrium, then $W$ must be the same as $W$. We also provide an alternate characterization of this space in terms of `generalized' marginal contributions, which is more appealing from the point of view of computational tractability. A possibly surprising consequence of our result is that, in order to guarantee equilibrium existence in all games with any fixed local welfare functions, it is \textitnecessary to work within the class of potential games.

Broadcast signcryption enables the broadcaster to simultaneously encrypt and sign the content meant for a specific set of users in a single logical step. It provides a very efficient solution to the dual problem of achieving confidentiality and authentication during content distribution. Among other alternatives, ID-based schemes are arguably the best suited for its implementation in wireless ad-hoc networks because of the unique advantage that they provide - any unique, publicly available parameter of a user can be his public key, which eliminates the need for a complex public key infrastructure. In 2004, Bohio et al. proposed an ID-based broadcast signcryption (IBBSC) scheme which achieves constant ciphertext size. They claim that their scheme provides both message authentication and confidentiality, but do not give formal proofs. In this paper, we demonstrate how a legitimate user of the scheme can forge a valid signcrypted ciphertext, as if generated by the broadcaster. Moreover, we show that their scheme is not IND-CCA secure. Following this, we propose a fix for Bohio et al.'s scheme, and formally prove its security under the strongest existing security models for broadcast signcryption (IND-CCA2 and EUF-CMA). While fixing the scheme, we also improve its efficiency by reducing the ciphertext size to two elements compared to three.