The Sanctuary mobile code system includes security mechanisms for protecting mobile agents from malicious servers as well as mechanisms for protecting mobile agent servers from malicious mobile code. To protect remotely executed mobile code, we integrate several key approaches: (1) security attributes certification to enable mobile code to avoid nodes in the agent-server network that are untrustworthy, as determined by user-centric security policies; (2) forward secure cryptography to improve detection of malicious tampering by servers; and (3) defining separate roles for agent author and agent owner, which justifies restricted delegation and external reference monitors with owner-provided agents to limit potential damage caused by buggy or compromised agent code. Simply put, we enable mobile code to avoid trouble when possible, and to detect trouble when it is unavoidable. We examine security-aware itinerary planning as a means to supplement these approaches, and describe our analysis of this problem. Our server uses well known approaches to defend itself from malicious code, and custom extensions that address the security needs of the mobile code itself. This paper describes our mechanisms and how they are integrated into the Sanctuary mobile code system.

Pre-2018 CSE ID: CS2002-0731

The practice of free-riding -- consuming service without providing equivalent service in return -- is a well-documented problem in contemporary peer-to-peer (P2P) networks that undermines the key advantages of service distribution, including scalability, availability and robust ness under attack. Existing approaches to the free-riding problem fall into two rough categories: reputation systems and commerce systems. To a first approximation, reputation systems appear better suited to managing actively greedy users in a reactive fashion, while commerce systems are more natural for pro-actively implementing appropriate incentives among passively self-interested users. We believe this l atter property represents a more pressing requirement for large-scale peer-to-peer systems and consequently focus on the commerce system approach. We propose in this work a design for the technical infrastructure necessary to implement a commerce-based resource sharing policy. There are two key components to any such infrastructure: an accounting mechanism to securely store the currency held by individual users and a settlement mechanism to fairly exchange currency for services. Traditionally, such systems have relied on the use of a single trusted third-party. Such a centralized solution, however, is at odds with the goals of P2P networks, which are by their nature highly distributed. Instead, we offer an alternative design that hinges on an accounting scheme based on the use of a distributed set of peers as accountants providing accounting functionality for each user in the system. We also propose several settlement protocols that leverage this accounting facility. Finally, we show that our design distributes accounting and settlement functions widely, providing powerful incentives without depending on a centralized trusted third-party to mediate each transaction.

Pre-2018 CSE ID: CS2003-0751