Device drivers typically execute in supervisor mode and thus must be fully trusted. This paper describes how to move them out of the trusted computing base, by running them without supervisor privileges and constraining their interactions with hardware devices. An implementation of this approach in the Nexus operating system executes drivers in user space, leveraging hardware isolation and checking their behavior against a safety specification. These Nexus drivers have performance comparable to inkernel, trusted drivers, with a level of CPU overhead acceptable for most applications. For example, the monitored driver for an Intel e1000 Ethernet card has throughput comparable to a trusted driver for the same hardware under Linux. And a monitored driver for the Intel i810 sound card provides continuous playback. Drivers for a disk and a USB mouse have also been moved successfully to operate in user space with safety specifications. 1

Many existing peer-to-peer content distribution networks (CDNs) such as Na Kika, CoralCDN, and CoDeeN are deployed on PlanetLab, a relatively trusted environment. But scaling them beyond this trusted boundary requires protecting against content corruption by untrusted replicas. This paper presents Repeat and Compare, a system for ensuring content integrity in untrusted peer-to-peer CDNs even when replicas dynamically generate content. Repeat and Compare detects misbehaving replicas through attestation records and sampled repeated execution. Attestation records, which are included in responses, cryptographically bind replicas to their code, inputs, and dynamically generated output. Clients then forward a fraction of these records to randomly selected replicas acting as verifiers. Verifiers, in turn, reliably identify misbehaving replicas by locally repeating response generation and comparing their results with the attestation records. We have implemented our system on top of Na Kika. We quantify its detection guarantees through probabilistic analysis and show through simulations that a small sample of forwarded records is sufficient to effectively and promptly cleanse a CDN, even if large fractions of replicas or verifiers are misbehaving. 1

We describe a new design for authorization in operating systems in which applications are first-class entities. In this design, principals reflect application identities. Access control lists are patterns that recognize principals. We present a security model that embodies this design in an experimental operating system, and we describe the implementation of our design and its performance in the context of this operating system. Categories and Subject Descriptors

Security modifications to legacy network protocols are expensive and disruptive. This paper outlines an approach, based on external security monitors, for securing legacy protocols by deploying additional hosts that locally monitor the inputs and outputs of each host executing the protocol, check the behavior of the host against a safety specification, and communicate using an overlay to alert other hosts about invalid behavior and to initiate remedial actions. Trusted computing hardware provides the basis for trust in external security monitors. This paper applies this approach to secure the Border Gateway Protocol, yielding an external security monitor called N-BGP. N-BGP can accurately monitor a BGP router using commodity trusted computing hardware. Deploying N-BGP at a random 10 % of BGP routers is sufficient to guarantee the security of 80 % of Internet routes where both endpoints are monitored by N-BGP. Overall, external security monitors secure the routing infrastructure using trusted computing hardware and construct a security plane for BGP without having to modify the large base of installed routers and servers. 1

the Grants No. (NSC95-main) and No. (NSC95-org), and by gifts from AMD and Intel.

This paper presents the design and implementation of NetQuery, a knowledge plane for federated networks such as the Internet. In such networks, not all administrative domains will generate information that an application can trust and many administrative domains may have restrictive policies on disclosing network information. Thus, both the trustworthiness and accessibility of network information pose obstacles to effective reasoning. NetQuery employs trustworthy computing techniques to facilitate reasoning about the trustworthiness of information contained in the knowledge plane while preserving confidentiality guarantees for operator data. By characterizing information disclosure between operators, NetQuery enables remote verification of advertised claims and contractual stipulations; this enables new applications because network guarantees can span administrative boundaries. We have implemented NetQuery, built several NetQuery-enabled devices, and deployed applications for cloud datacenters, enterprise networks, and the Internet. Simulations, testbed experiments, and a deployment on a departmental network indicate NetQuery can support hundreds of thousands of operations per second and can thus scale to large ISPs.

Nexus Authorization Logic (NAL) provides a principled basis for specifying and reasoning about credentials and authorization policies. It extends prior access control logics that are based on “says ” and “speaks for” operators. NAL enables authorization of access requests to depend on (i) the source or pedigree of the requester, (ii) the outcome of any mechanized analysis of the requester, or (iii) the use of trusted software to encapsulate or modify the requester. To illustrate the convenience and expressive power of this approach to authorization, a suite of document-viewer applications was implemented to run on the Nexus operating system. One of the viewers enforces policies that concern the integrity of excerpts that a document contains; another viewer enforces confidentiality policies specified by labels tagging blocks of text.

Nexus Authorization Logic (NAL) provides a principled basis for specifying and reasoning about credentials and authorization policies. It extends prior access control logics based on “says and “speaksfor” operators, enabling within a single framework request authorization to depend on (i) the source or pedigree of the requester, (ii) the outcome of performing an analysis on the requester, or (iii) the use of trusted software to encapsulate or modify the requester. Prototype document-viewer applications that enforce integrity and confidentiality of document contents—all implemented on the Nexus operating system—illustrate the convenience and expressive power of this approach to authorization.

External security monitors (ESMs) are a new network component for securing legacy protocols without requiring modifications to existing hardware, software, or the protocol. An ESM is an additional host that checks each message sent by a legacy host against a safety specification. ESMs use trusted hardware to assure remote principals that the safety specification is being enforced; ESMs use an overlay network to alert each other about invalid behavior and to initiate remedial actions. N-BGP is an ESM for securing the Internet’s Border Gateway Protocol (BGP). When run on commodity hardware, N-BGP is fast enough to monitor a production BGP router. And deploying N-BGP at a random 10 % of autonomous systems in the Internet suffices to guarantee security for 80 % of Internet routes where both endpoints are monitored by N-BGP.