Murillo Pontual

On the management of user obligations

This paper is part of a project investigating authorization systems that assign obligations to users. We are particularly interested in obligations that require authorization to be performed and that, when performed, may modify the authorization state. In this context, a user may incur an obligation she is unauthorized to perform. Prior work has introduced a property of the authorization system state that ensures users will be authorized to fulfill their obligations. We call this property accountability because users that fail to perform authorized obligations are accountable for their non-performance. While a reference monitor can mitigate violations of accountability, it cannot prevent them entirely. This paper presents techniques to be used by obligation system managers to restore accountability. We introduce several notions of dependence among pending obligations that must be considered in this process. We also introduce a novel notion we call obligation pool slicing, owing to its similarity to program slicing. An obligation pool slice identifies a set of obligations that the administrator may need to consider when applying strategies proposed here for restoring accountability. The paper also presents the system architecture of an authorization system that incorporates obligations that can require and affect authorizations.

An Assessment of Remote Laboratory Experiments in Radio Communication

Todays electrical and computer engineering graduates need marketable skills to work with electronic devices. Hands-on experiments prepare students to deal with real-world problems and help them to comprehend theoretical concepts and relate these to practical tasks. However, shortage of equipment, high costs, and a lack of human resources for laboratory maintenance and assistance decrease the implementation capacity of hands-on training laboratories. At the same time, the Internet has become a common networking medium and is increasingly used to enhance education. In addition, at many sites, existing experimental systems are typically underutilized. These cost and efficient exploitation constraints can be resolved by the use of remote laboratories accessible through the Internet that can be shared and used at flexible times and from various locations. This paper is a description of a systematic assessment effort of the efficiency of remote laboratories in radio communication. The labs are offered to graduate and undergraduate students, and hands-on and remote experiences are compared. A dedicated remote experimentation system, eComLab, was developed to support the effort.

Toward practical authorization-dependent user obligation systems

Many authorization system models include some notion of obligation. Little attention has been given to user obligations that depend on and affect authorizations. However, to be usable, the system must ensure users have the authorizations they need when their obligations must be performed. Prior work in this area introduced accountability properties that ensure failure to fulfill obligations is not due to lack of required authorizations. That work presented inconclusive and purely theoretical results concerning the feasibility of maintaining accountability in practice. The results of the current paper include algorithms and performance analysis that support the thesis that maintaining accountability in a reference monitor is reasonable in many applications.

Ensuring authorization privileges for cascading user obligations

User obligations are actions that the human users are required to perform in some future time. These are common in many practical access control and privacy and can depend on and affect the authorization state. Consequently, a user can incur an obligation that she is not authorized to perform which may hamper the usability of a system. To mitigate this problem, previous work introduced a property of the authorization state, accountability, which requires that all the obligatory actions to be authorized when they are attempted. Although, existing work provides a specific and tractable decision procedure for a variation of the accountability property, it makes a simplified assumption that no cascading obligations may happen, i.e., obligatory actions cannot further incur obligations. This is a strong assumption which reduces the expressive power of past models, and thus cannot support many obligation scenarios in practical security and privacy policies. In this work, we precisely specify the strong accountability property in the presence of cascading obligations and prove that deciding it is NP-hard. We provide for several special yet practical cases of cascading obligations (i.e., repetitive, finite cascading, etc.) a tractable decision procedure for accountability. Our experimental results illustrate that supporting such special cases is feasible in practice.

The privacy in the time of the internet: secrecy vs transparency

In the current time of the Internet, specifically with the emergence of social networking, people are sharing both sensitive and non-sensitive information among each other without understanding its consequences. Federal regulations exist to mandate how sensitive information (e.g., SSN, health records, etc.) of a person can be shared (or, used) by organizations. However, there are no established norms or practices regarding how information that is deemed to be not sensitive may be used or shared. Furthermore, for the sake of transparency, different organizations reveal small amounts of non-sensitive information (i.e., photos, salaries, work hours, size of the houses, etc.) about their clients or employees. Although such information seems insignificant, the aggregation of it can be used to create a partial profile of a person which can later be used by malicious parties for robbery, extortion, kidnapping, etc. The goal of this work is to create awareness by demonstrating that it is plausible to create such a partial profile of a person just by crawling the Internet. For this, we have developed an open source framework that generates batch crawlers to create partial profiles of individuals. We also show empirical comparisons of the amount of information that can be gathered by using free and also paid websites.