Eric Cronin

Constrained mirror placement on the Internet

Web content providers and content distribution network (CDN) operators often set up mirrors of popular content to improve performance. Due to the scale and decentralized administration of the Internet, companies have a limited number of sites (relative to the size of the Internet) where they can place mirrors. We formalize the mirror placement problem as a case of constrained mirror placement, where mirrors can only be placed on a preselected set of candidates. We study performance improvement in terms of client round-trip time (RTT) and server load when clients are clustered by the autonomous systems (AS) in which they reside. Our results show that, regardless of the mirror placement algorithm used, for only a surprisingly small range of values there is an increase in the number of mirror sites (under the constraint) effective in reducing the client to server RTT and server load. In this range, we show that greedy placement performs the best.

An Efficient Synchronization Mechanism for Mirrored Game Architectures

Existing online multiplayer games typically use a client-server model, which introduces added latency as well as a single bottleneck and single point of failure to the game. Distributed multiplayer games minimize latency and remove the bottleneck, but require special synchronization mechanisms to provide a consistent game for all players. Current synchronization methods have been borrowed from distributed military simulations and are not optimized for the requirements of fast-paced multiplayer games. In this paper we present a new synchronization mechanism, trailing state synchronization (TSS), which is designed around the requirements of distributed first-person shooter games.We look at TSS in the environment of a mirrored game architecture, which is a hybrid between traditional centralized architectures and the more scalable peer-to-peer architectures. Mirrored architectures allow for improved performance compared to client-server architectures while at the same time allowing for a greater degree of centralized administration than peer-to-peer architectures.We evaluate the performance of TSS and other synchronization methods through simulation and examine heuristics for selecting the synchronization delays needed for TSS.

Analysis of security vulnerabilities in the movie production and distribution process

Unauthorized copying of movies is a major concern for the motion picture industry. While unauthorized copies of movies have been distributed via portable physical media for some time, low-cost, high-bandwidth Internet connections and peer-to-peer file sharing networks provide highly efficient distribution media. Many movies are showing up on file sharing networks shortly after, and in some cases prior to, theatrical release. It has been argued that the availability of unauthorized copies directly affects theater attendance and DVD sales, and hence represents a major financial threat to the movie industry. Our research attempts to determine the source of unauthorized copies by studying the availability and characteristics of recent popular movies in file sharing networks. We developed a data set of 312 popular movies and located one or more samples of 183 of these movies on file sharing networks, for a total of 285 movie samples. 77% of these samples appear to have been leaked by industry insiders. Most of our samples appeared on file sharing networks prior to their official consumer DVD release date. Indeed, of the movies that had been released on DVD as of the time of our study, only 5% first appeared after their DVD release date on a web site that indexes file sharing networks, indicating that consumer DVD copying currently represents a relatively minor factor compared with insider leaks. We perform a brief analysis of the movie production and distribution process and identify potential security vulnerabilities that may lead to unauthorized copies becoming available to those who may wish to redistribute them. Finally, we offer recommendations for reducing security vulnerabilities in the movie production and distribution process.

On the performance, feasibility, and use of forward-secure signatures

Forward-secure signatures (FSSs) have recently received much attention from the cryptographic theory community as a potentially realistic way to mitigate many of the difficulties digital signatures face with key exposure. However, no previous works have explored the practical performance of these proposed constructions in real-world applications, nor have they compared FSS to traditional, non-forward-secure, signatures in a non-asymptotic way.We present an empirical evaluation of several FSS schemes that looks at the relative performance among different types of FSS as well as between FSS and traditional signatures. Our study provides the following contributions: first, a new methodology for comparing the performance of signature schemes, and second, a thorough examination of the practical performance of FSS. We show that for many cases the best FSS scheme has essentially identical performance to traditional schemes, and even in the worst case is only 2-4 times slower. On the other hand, we also show that if the wrong FSS configuration is used, the performance can be orders of magnitude slower. Our methodology provides a way to prevent such misconfigurations, and we examine common applications of digital signatures using it.We conclude that not only are forward-secure signatures a useful theoretical construct as previous works have shown, but they are also, when used correctly, a very practical solution to some of the problems associated with key exposure in real-world applications. Through our metrics and our reference implementation we provide the tools necessary for developers to efficiently use FSS.

Signaling vulnerabilities in wiretapping systems

Many law enforcement wiretap systems are vulnerable to simple, unilateral countermeasures that exploit the unprotected in-band signals passed between the telephone network and the collection system. This article describes the problem as well as some remedies and workarounds.

Provenance-aware secure networks

Network accountability and forensic analysis have become increasingly important, as a means of performing network diagnostics, identifying malicious nodes, enforcing trust management policies, and imposing diverse billing over the Internet. This has led to a series of work to provide better network support for accountability, and efficient mechanisms to trace packets and information flows through the Internet. In this paper, we make the following contributions. First, we show that network accountability and forensic analysis can be posed generally as data provenance computations and queries over distributed streams. In particular, one can utilize declarative networks with appropriate security and provenance extensions to provide a unified declarative framework for specifying, analyzing and auditing networks. Second, we propose a taxonomy of data provenance along multiple axes, and show that they map naturally to different use cases in networks. Third, we suggest techniques to efficiently compute and store network provenance, and provide an initial performance evaluation on the P2 declarative networking system with modifications to support authenticated communication and provenance.

Listen too closely and you may be confused

I’d like to shift views a little bit, and think about the problem that we usually focus on, which is building good defences, from the point of view of how to attack effectively. We tend to focus on the defending problem, for example, the confidentiality of my traffic, and in the mainstream and conservative approach to security that we all know and love we make very generous assumptions about the adversary: we are willing to assume that the adversary gets a copy of every packet we send, it can alter some of the bits in real time, and has unlimited computational power, etc. As a result of that conservative assumption, we ask to have solutions that assume that the network is unlimitedly hostile. And, if you want security, we must accept nothing less than end-to-end security, and if we don’t have to end-to-end security we simply assume that it is insecure, because it would be very silly to depend on anything less than this very reasonable conservative assumption.

Can they hear me now?: a security analysis of law enforcement wiretaps

Although modern communications services are susceptible to third-party eavesdropping via a wide range of possible techniques, law enforcement agencies in the US and other countries generally use one of two technologies when they conduct legally-authorized interception of telephones and other communications traffic. The most common of these, designed to comply with the 1994 Communications Assistance for Law Enforcement Act(CALEA), use a standard interface provided in network switches. This paper analyzes the security properties of these interfaces. We demonstrate that the standard CALEA interfaces are vulnerable to a range of unilateral attacks by the intercept target. In particular, because of poor design choices in the interception architecture and protocols, our experiments show it is practical for a CALEA-tapped target to overwhelm the link to law enforcement with spurious signaling messages without degrading her own traffic, effectively preventing call records as well as content from being monitored or recorded. We also identify stop-gap mitigation strategies that partially mitigate some of our identified attacks.

On the Reliability of Network Eavesdropping Tools

This paper analyzes the problem of intercepting Internet traffic from the eavesdropper’s point of view. It examines the reliability and accuracy of transcripts, and shows that obtaining “high fidelity” transcripts is harder than previously assumed. Even in highly favorable situations, such as capturing unencrypted traffic using standard protocols, simple — and entirely unilateral — countermeasures are shown to be sufficient to prevent accurate traffic analysis in many Internet interception configurations. In particular, these countermeasures were successful against every available eavesdropping system we tested. Central to our approach is a new class of “confusion” techniques, that unlike cryptography or steganography, do not require cooperation by the communicating parties and, in some cases, can be employed entirely by a third party who is not involved in the communication.

Measurable security through isotropic channels

This position paper proposes the use of special broadcast networks to achieve provable and measurable confidentiality of messages. We call these networks isotropic channels, broadcast channels in which receivers cannot reliably determine whether a given message originated from any particular sender and senders cannot prevent a message from reaching any particular receiver. As long as eavesdroppers cannot reliably (i.e., with probabilistic certainty) identify the sender of a message, honest parties can efficiently exchange messages with confidentiality that asymptotically approaches and in some cases reaches perfect secrecy. Even under incorrect assumptions regarding the degree of isotropism offered by a particular channel, a high measure of confidentiality can be efficiently achieved. This position paper additionally makes the case that isotropic channels already exist, and are, in fact, often used in practice. By leveraging isotropic techniques, measurable information theoretic security can be practically achieved.