Bridger Hahn

David Zage, Helen Xu, Thomas Kroeger et al.

Data security and availability for operational use are frequently seen as conflicting goals. Research on searchable encryption and homomorphic encryption are a start, but they typically build from encryption methods that, at best, provide protections based on problems assumed to be computationally hard. By contrast, data encoding methods such as secret sharing provide information-theoretic data protections. Archives that distribute data using secret sharing can provide data protections that are resilient to malicious insiders, compromised systems, and untrusted components. In this paper, we create the Serial Interpolation Filter, a method for storing and interacting with sets of data that are secured and distributed using secret sharing. We provide the ability to operate over set-oriented data distributed across multiple repositories without exposing the original data. Furthermore, we demonstrate the security of our method under various attacker models and provide protocol extensions to handle colluding attackers. The Serial Interpolation Filter provides information-theoretic protections from a single attacker and computationally hard protections from colluding attackers.

Nolan Donoghue, Bridger Hahn, Helen Xu et al.

Access to network traffic records is an integral part of recognizing and addressing network security breaches. Even with the increasing sophistication of network attacks, basic network events such as connections between two IP addresses play an important role in any network defense. Given the duration of current attacks, long-term data archival is critical but typically very little of the data is ever accessed. Previous work has provided tools and identified the need to trace connections. However, traditional databases raise performance concerns as they are optimized for querying rather than ingestion. The study of write-optimized data structures (WODS) is a new and growing field that provides a novel approach to traditional storage structures (e.g., B-trees). WODS trade minor degradations in query performance for significant gains in the ability to quickly insert more data elements, typically on the order of 10 to 100 times more inserts per second. These efficient, out-of-memory data structures can play a critical role in enabling robust, long-term tracking of network events. In this paper, we present TWIAD, the Write-optimized IP Address Database. TWIAD uses a write-optimized B-tree known as a B ε tree to track all IP address connections in a network traffic stream. Our initial implementation focuses on utilizing lower cost hardware, demonstrating that basic long-term tracking can be done without advanced equipment. We tested TWIAD on a modest desktop system and showed a sustained ingestion rate of about 20,000 inserts per second.

Bridger Hahn, Rishab Nithyanand, Phillipa Gill et al.

The Internet has become a critical communication infrastructure for citizens to organize protests and express dissatisfaction with their governments. This fact has not gone unnoticed, with governments clamping down on this medium via censorship, and circumvention researchers working to stay one step ahead. In this paper, we explore a promising new avenue for covert channels: real-time strategy-video games. Video games have two key features that make them attractive cover protocols for censorship circumvention. First, due to the popularity of gaming platforms such as Steam, there are a lot of different video games, each with their own protocols and server infrastructure. Users of video-game-based censorship-circumvention tools can therefore diversify across many games, making it difficult for the censor to respond by simply blocking a single cover protocol. Second, games in the same genre have many common features and concepts. As a result, the same covert channel framework can be easily adapted to work with many different games. This means that circumvention tool developers can stay ahead of the censor by creating a diverse set of tools and by quickly adapting to blockades created by the censor. We demonstrate the feasibility of this approach by implementing our coding scheme over two real-time strategy-games (including a very popular closed-source game). We evaluate the security of our system prototype -- Castle -- by quantifying its resilience to a censor-adversary, its similarity to real game traffic, and its ability to avoid common pitfalls in covert channel design. We use our prototype to demonstrate that our approach can provide throughput which is amenable to transfer of textual data, such at e-mail, SMS messages, and tweets, which are commonly used to organize political actions.