Drawing on recent results in the industrial organization literature (Carvajal et al. 2013), we derive non-parametric tests of the tragedy of the commons. Our approach allows group output to be any arbitrarily concave, differentiable function of total inputs and for individual exploiters of the resource to have any arbitrary convex, differentiable cost of supplying inputs. We show that observed ...

Delegation is a widely used and widely studied mechanism in access control systems. Delegation enables an authorized entity to nominate another entity as its authorized proxy for the purposes of access control. Existing delegation mechanisms tend to rely on manual processes initiated by end-users. We believe that systems in which the set of available, authorized entities fluctuates considerably...

Warning signals generated by sirens of authorized emergency vehicles should be audible and recognizable to all road users. Currently, there is no legislation in Poland defining sound pressure levels (SPLs) of audible warning signals generated by sirens of authorized emergency vehicles. Measured A-weighted SPLs of those signals range between 104 and 108 dB. While for road users, an audible warni...

This paper deals with threshold public-key encryption which allows a pool of players to decrypt a ciphertext if a given threshold of authorized players cooperate. We generalize this primitive to the dynamic setting, where any user can dynamically join the system, as a possible recipient; the sender can dynamically choose the authorized set of recipients, for each ciphertext; and the sender can ...

This paper documents changes in the rates and characteristics of undercover police investigations against child sexual exploiters on the Internet. Telephone interviews were conducted with law enforcement officials about a nationally representative sample of cases ending in arrest for an Internet-related sex crime against a minor in 2000 and 2006. The survey found a 280% increase in arrests of o...

A study was performed to investigate a domain for a mobile and social service, where a web of social trails is overlaid over a physical space. Using a method inspired by work of the city planner Kevin Lynch, 20 subjects were interviewed about their experiences, activities, movements and habits related to a specific shopping mall. Design implications for the service were drawn from subjects’ ske...

Programmers have traditionally been passive users of compilers, rather than active exploiters of their transformational abilities. This paper presents MAGIK, a system that allows programmers to easily and modularly incorporate applicationspecific extensions into the compilation process. The MAGIK system gives programmers two significant capabilities. First, it provides mechanisms that implement...