Matthew Spindel Burnside

The Untrusted Computer Problem and Camera-Based Authentication

The use of computers in public places is increasingly common in everyday life. In using one of these computers, a user is trusting it to correctly carry out her orders. For many transactions, particularly banking operations, blind trust in a public terminal will not satisfy most users. In this paper the aim is therefore to provide the user with authenticated communication between herself and a remote trusted computer, via the untrusted computer.After defining the authentication problem that is to be solved, this paper reduces it to a simpler problem. Solutions to the simpler problem are explored in which the user carries a trusted device with her. Finally, a description is given of two camera-based devices that are being developed.

Proxy-based security protocols in networked mobile devices

We describe a resource discovery and communication system designed for security and privacy. All objects in the system, e.g., appliances, wearable gadgets, software agents, and users have associated trusted software proxies that either run on the appliance hardware or on a trusted computer. We describe how security and privacy are enforced using two separate protocols: a protocol for secure device-to-proxy communication, and a protocol for secure proxy-to-proxy communication. Using two separate protocols allows us to run a computationally-inexpensive protocol on impoverished devices, and a sophisticated protocol for resource authentication and communication on more powerful devices.We detail the device-to-proxy protocol for lightweight wireless devices and the proxy-to-proxy protocol which is based on SPKI/SDSI (Simple Public Key Infrastructure / Simple Distributed Security Infrastructure). A prototype system has been constructed, which allows for secure, yet efficient, access to networked, mobile devices. We present a quantitative evaluation of this system using various metrics.

Low latency anonymity with mix rings

We introduce mix rings, a novel peer-to-peer mixnet architecture for anonymity that yields low-latency networking compared to existing mixnet architectures. A mix ring is a cycle of continuous-time mixes that uses carefully coordinated cover traffic and a simple fan-out mechanism to protect the initiator from timing analysis attacks. Key features of the mix ring architecture include decoupling path creation from data transfer, and a mechanism to vary the cover traffic rate over time to prevent bandwidth overuse. We analyze the architecture with respect to other peer-to-peer anonymity systems – onion routing and batching mixnets – and we use simulation to demonstrate performance advantages of nearly 40% over batching mixnets while protecting against a wider variety of adversaries than onion routing.

Cryptography as an operating system service: A case study

Cryptographic transformations are a fundamental building block in many security applications and protocols. To improve performance, several vendors market hardware accelerator cards. However, until now no operating system provided a mechanism that allowed both uniform and efficient use of this new type of resource.We present the OpenBSD Cryptographic Framework (OCF), a service virtualization layer implemented inside the operating system kernel, that provides uniform access to accelerator functionality by hiding card-specific details behind a carefully designed API. We evaluate the impact of the OCF in a variety of benchmarks, measuring overall system performance, application throughput and latency, and aggregate throughput when multiple applications make use of it.We conclude that the OCF is extremely efficient in utilizing cryptographic accelerator functionality, attaining 95% of the theoretical peak device performance and over 800 Mbps aggregate throughput using 3DES. We believe that this validates our decision to opt for ease of use by applications and kernel components through a uniform API and for seamless support for new accelerators. Furthermore, our evaluation points to several bottlenecks in system and operating system design: data copying between user and kernel modes, PCI bus signaling inefficiency, protocols that use small data units, and single-threaded applications. We identify some of these limitations through a set of measurements focusing on application-layer cryptographic protocols such as SSL. We offer several suggestions for improvements and directions for future work. We provide experimental evidence of the effectiveness of a new approach which we call operating system shortcutting. Shortcutting can improve the performance of application-layer cryptographic protocols by 27% with very small changes to the kernel.

Accelerating application-level security protocols

We present a minimal extension to the BSD socket layer that can improve the performance of application-level security protocols, such as SSH or SSL/TLS, by 10%, when hardware cryptographic accelerators are available in the system. Applications specify what cryptographic transforms must be applied to incoming and outgoing data frames, and such processing is applied by the operating system itself (exploiting hardware accelerators) when the application sends or receives data. Under this scheme, we can reduce the number of system calls and context switches by 50%, and the amount of data copying by 66%. We describe our prototype implementation for the openBSD system and quantify its performance implications. We conclude with a discussion of further possible performance improvements that our approach enables.

Access-controlled resource discovery for pervasive networks

Networks of the future will be characterized by a variety of computational devices that display a level of dynamism not seen in traditional wired networks. Because of the dynamic nature of these networks, resource discovery is one of the fundamental problems that must be faced. While resource discovery systems are not a novel concept, securing these systems in an efficient and scalable way is challenging. This paper describes the design and implementation of an architecture for access-controlled resource discovery. This system achieves this goal by integrating access control with the Intentional Naming System (INS), a resource discovery and service location system. The integration is scalable, efficient, and fits well within a proxy-based security framework designed for dynamic networks. We provide performance experiments that show how our solution outperforms existing schemes. The result is a system that provides secure, access-controlled resource discovery that can scale to large numbers of resources and users.

High-speed I/O: the operating system as a signalling mechanism

The design of modern operating systems is based around the concept of memory as a cache for data that flows between applications, storage, and I/O devices. With the increasing disparity between I/O bandwidth and CPU performance, this architecture exposes the processor and memory subsystems as the bottlenecks to system performance. Furthermore, this design does not easily lend itself to exploitation of new capabilities in peripheral devices, such as programmable network cards or special-purpose hardware accelerators, capable of card-to-card data transfers.We propose a new operating system architecture that removes the memory and CPU from the data path. The role of the operating system becomes that of data-flow management, while applications operate purely at the signaling level. This design parallels the evolution of modern network routers, and has the potential to enable high-performance I/O for end-systems, as well as fully exploit recent trends in programmability of peripheral (I/O) devices.

Bloodhound: Searching Out Malicious Input in Network Flows for Automatic Repair Validation

Many current systems security research efforts focus on mechanisms for Intrusion Prevention and Self-Healing Software. Unfortunately, such systems find it difficult to gain traction in many deployment scenarios. For self-healing techniques to be realistically employed, system owners and administrators must have enough confidence in the quality of a generated fix that they are willing to allow its automatic deployment. In order to increase the level of confidence in these systems, the efficacy of a ’fix’ must be tested and validated after it has been automatically developed, but before it is actually deployed. Due to the nature of attacks, such verification must proceed automatically. We call this problem Automatic Repair Validation (ARV). As a way to illustrate the difficulties faced by ARV, we propose the design of a system, Bloodhound, that tracks and stores malicious network flows for later replay in the validation phase for self-healing software.

Arachne: Integrated Enterprise Security Management

Security policies are a key component in protecting enterprise networks. There are many defensive options available to these policies, but current mechanically-enforced security policies are limited to traditional admission-based access control. There are defensive capabilities available that include logging, firewalls, honeypots, rollback/recovery, and intrusion detection systems, but policy enforcement is essentially limited to allow/deny semantics. Furthermore, access-control mechanisms operate independently on each service, which often leads to inconsistent or incorrect application of the intended system-wide policy. To begin to solve these problems, we propose a new system for defense-in-depth using global security policies. Under a global security policy, every policy decision is made with near-global knowledge, and re-evaluated as global knowledge changes, given an initial configuration provided by the administrator. Using a variety of actuators, we make the full array of defensive capabilities available to the global policy. We outline our proposal for enterprise-wide security policies, explore the design space, and discuss Arachne, our prototype implementation.

Path-Based Access Control for Enterprise Networks

Enterprise networks are ubiquitious and increasingly complex. The mechanisms for defining security policies in these networks have not kept up with the advancements in networking technology. In most cases, system administrators define policies on a per-application basis, and subsequently, these policies do not interact. For example, there is no mechanism that allows a web server to communicate decisions based on its ruleset to a firewall in front of it, even though decisions being made at the web server may be relevant to decisions at the firewall. In this paper, we describe a path-based access control system for service-oriented architecture (SOA)-style networks which allows services to pass access-control-related information to neighboring services, as the services process requests from outsiders and from each other. Path-based access control defends networks against a class of attacks wherein individual services make correct access control decisions but the resulting global network behavior is incorrect. We demonstrate the system in two forms, using graph-based policies and by leveraging the KeyNote trust management system.