Jamie Morgenstern

Security-typed programming within dependently typed programming

Several recent security-typed programming languages, such as Aura, PCML5, and Fine, allow programmers to express and enforce access control and information flow policies. In this paper, we show that security-typed programming can be embedded as a library within a general-purpose dependently typed programming language, Agda. Our library, Aglet, accounts for the major features of existing security-typed programming languages, such as decentralized access control, typed proof-carrying authorization, ephemeral and dynamic policies, authentication, spatial distribution, and information flow. The implementation of Aglet consists of the following ingredients: First, we represent the syntax and proofs of an authorization logic, Garg and Pfennings BL0, using dependent types. Second, we implement a proof search procedure, based on a focused sequent calculus, to ease the burden of constructing proofs. Third, we represent computations using a monad indexed by pre- and post-conditions drawn from the authorization logic, which permits ephemeral policies that change during execution. We describe the implementation of our library and illustrate its use on a number of the benchmark examples considered in the literature.

Simple Auctions with Simple Strategies

We introduce single-bid auctions as a new format for combinatorial auctions. In single-bid auctions, each bidder submits a single real-valued bid for the right to buy items at a fixed price. Contrary to other simple auction formats, such as simultaneous or sequential single-item auctions, bidders can implement no-regret learning strategies for single-bid auctions in polynomial time. Price of anarchy bounds for correlated equilibria concepts in single-bid auctions therefore have more bite than their counterparts for auctions and equilibria for which learning is not known to be computationally tractable (or worse, known to be computationally intractable [Cai and Papadimitriou 2014; Dobzinski et al. 2015] this end, we show that for any subadditive valuations the social welfare at equilibrium is an O(log m)-approximation to the optimal social welfare, where

Strategic Network Formation with Attack and Immunization

m

Simple Mechanisms for Agents with Complements

is the number of items. We also provide tighter approximation results for several subclasses. Our welfare guarantees hold for Nash equilibria and no-regret learning outcomes in both Bayesian and complete information settings via the smooth-mechanism framework. Of independent interest, our techniques show that in a combinatorial auction setting, efficiency guarantees of a mechanism via smoothness for a very restricted class of cardinality valuations extend, with a small degradation, to subadditive valuations, the largest complement-free class of valuations.

Fairness Incentives for Myopic Agents

Strategic network formation arises in settings where agents receive some benefit from their connectedness to other agents, but also incur costs for forming these links. We consider a new network formation game that incorporates an adversarial attack, as well as immunization or protection against the attack. An agents network benefit is the expected size of her connected component post-attack, and agents may also choose to immunize themselves from attack at some additional cost. Our framework can be viewed as a stylized model of settings where reachability rather than centrality is the primary interest as in many technological networks such as the Internet, and vertices may be vulnerable to attacks such as viruses, but may also reduce risk via potentially costly measures such as an anti-virus software. Our main theoretical contributions include a strong bound on the edge density at equilibrium. In particular, we show that under a very mild assumption on the adversarys attack model, every equilibrium network contains at most only

A proof-carrying file system with revocable and use-once certificates

2n-4

On the Pseudo-Dimension of Nearly Optimal Auctions

2n-4 edges for