Stephen T. Kent

Hash-based IP traceback

The design of the IP protocol makes it difficult to reliably identify the originator of an IP packet. Even in the absence of any deliberate attempt to disguise a packets origin, wide-spread packet forwarding techniques such as NAT and encapsulation may obscure the packets true source. Techniques have been developed to determine the source of large packet flows, but, to date, no system has been presented to track individual packets in an efficient, scalable fashion.We present a hash-based technique for IP traceback that generates audit trails for traffic within the network, and can trace the origin of a single IP packet delivered by the network in the recent past. We demonstrate that the system is effective, space-efficient (requiring approximately 0.5% of the link capacity per unit time in storage), and implementable in current or next-generation routing hardware. We present both analytic and simulation results showing the systems effectiveness.

Secure Border Gateway Protocol (S-BGP)

The Border Gateway Protocol (BGP), which is used to distribute routing information between autonomous systems (ASes), is a critical component of the Internets routing infrastructure. It is highly vulnerable to a variety of malicious attacks, due to the lack of a secure means of verifying the authenticity and legitimacy of BGP control traffic. This paper describes a secure, scalable, deployable architecture (S-BGP) for an authorization and authentication system that addresses most of the security problems associated with BGP. The paper discusses the vulnerabilities and security requirements associated with BGP, describes the S-BGP countermeasures, and explains how they address these vulnerabilities and requirements. In addition, this paper provides a comparison of this architecture to other approaches that have been proposed, analyzes the performance implications of the proposed countermeasures, and addresses operational issues.

Single-packet IP traceback

The design of the IP protocol makes it difficult to reliably identify the originator of an IP packet. Even in the absence of any deliberate attempt to disguise a packets origin, widespread packet forwarding techniques such as NAT and encapsulation may obscure the packets true source. Techniques have been developed to determine the source of large packet flows, but, to date, no system has been presented to track individual packets in an efficient, scalable fashion. We present a hash-based technique for IP traceback that generates audit trails for traffic within the network, and can trace the origin of a single IP packet delivered by the network in the recent past. We demonstrate that the system is effective, space efficient (requiring approximately 0.5% of the link capacity per unit time in storage), and implementable in current or next-generation routing hardware. We present both analytic and simulation results showing the systems effectiveness.

Security Mechanisms in High-Level Network Protocols

The implications of adding security mechanisms to high-level network protocols operating in an open-system environment are analyzed. First the threats to security that may arise in such an environment are described, and then a set of goals for communications security measures is established. This is followed by a brief description of the two basic approaches to communications security, link-oriented measures and end-to-end measures, which concludes that end-to-end measures are more appropriate in an open-system environment. Next, relevant properties of data encryption--the fundamental technique on which all communications security mechanisms are based--are discussed. The remainder of the paper describes ho~w end-to-end measures can be used to achieve each of the security goals previously established.

Internet Privacy Enhanced Mail

Privacy Enhanced Mail (PEM) consists of extensions to existing message processing software plus a key management infrastructure. These combine to provide users with a facility in which message confidentiality, authenticity, and integrity can be effected. PEM is compatible with RFC 822 message processing conventions and is transparent to SMTP mail relays. PEM uses symmetric cryptography — for example, the Data Encryption Standard (DES) — to provide (optional) encryption of messages. Although the RFCs permit the use of either symmetric or asymmetric (public key) cryptography (for instance, the RSA cryptosystem) to distribute symmetric keys, the RFCs strongly recommend the use of asymmetric cryptography for this purpose and to generate and validate digital signatures for messages and certificates. Public key management in PEM is based on the use of certificates as defined by the CCITT Directory Authentication Framework [CCIT88c]. A public key certification hierarchy for PEM is being established by the Internet Society. This certification hierarchy supports universal authentication of PEM users, under various policies, without the need for prior bilateral agreements among users or organizations with which the users may be affiliated.

Domain based Internet security policy management

As security devices and protocols become widely used on the Internet, the task of managing and processing communication security policies grows steeply in its complexity. This paper presents a scaleable, robust, secure distributed system that can manage communication security policies associated with multiple network domains and resolving the policies-esp. those that specify the use of IP-AH/ESP security protocols-into security requirements for inter-domain communication. Technology innovation includes a formal model for IPsec policy specification and resolution, a platform independent policy specification language and a distributed policy server system. The formal model consists of a hierarchical domain model for IPsec policy enforcement and a lattice model of IPsec policy semantics. The policy specification language enables users to specify IPsec policies using the formal model regardless of the make of the security devices. The policy servers maintain the security policies in a distributed database, and negotiate the security associations for protecting inter-domain communication. Both the policy database and the policy exchange protocol are protected from passive and active attacks. Several UNIX implementations are available for non-commercial uses.

Hardware support for a hash-based IP traceback

The Source Path Isolation Engine (SPIE) is a system capable of tracing a single IP packet to its point of origin or point of ingress into a network. SPIE supports tracing by scoring a few bits of unique information about each packet for a period of time as the packets traverse the network. Software implementations of SPIE can trace packets through networks comprised of slow-to-medium speed routers (up to OC-12), but higher-speed routers (OC-48 and faster) require hardware support. In this paper, we discuss these hardware design aspects of SPIE. Most of the hardware resides in a self-contained SPIE processing unit, which may be implemented in a line card form factor for insertion into the router itself or as a stand-alone unit that connects to the router through an external interface.

A public-key based secure mobile IP

The need of scaleable key management support for Mobile IP, especially the route‐optimized Mobile IP, is well known. In this paper, we present the design and the implementation of a public key management system that can be used with IETF basic and route optimized Mobile IP. The system, known as the Mobile IP Security (MoIPS) system, was built upon a DNS based X.509 Public Key Infrastructure and the innovation in cross certification and zero‐message key generation. The system can supply cryptographic keys for authenticating Mobile IPv.4 location management messages and establishing IPSec tunnels for Mobile IP redirected packets. It can also be used to augment firewall traversal of Mobile IP datagrams. A FreeBSD UNIX implementation of the MoIPS prototype is available for non‐commercial uses.

Securing the Border Gateway Protocol: A Status Update

The Border Gateway Protocol (BGP) is a critical component of the Internet routing infrastructure, used to distribute routing information between autonomous systems (ASes). It is highly vulnerable to a variety of malicious attacks and benign operator errors. Under DARPA sponsorship, BBN has developed a secure version of BGP (S-BGP) that addresses most of BGP’s architectural security problems. This paper reviews BGP vulnerabilities and their implications, derives security requirements based on the semantics of the protocol, and describes the S-BGP architecture. Refinements to the original S-BGP design, based on interactions with ISP operations personnel and further experience with a prototype implementation are presented, including a heuristic for significantly improving performance. The paper concludes with a comparison of S-BGP to other proposed approaches.

Securing the Nimrod routing architecture

This paper describes the work undertaken to secure Nimrod, a complex and sophisticated routing system that unifies interior and exterior routing functions. The focus of this work is countering attacks that would degrade or deny service to network subscribers. The work began with an analysis of security requirements for Nimrod, based on a hybrid approach that refines top-down requirements generation with an understanding of attack scenarios and the capabilities and limitations of countermeasures. The countermeasures selected for use here include several newly developed sequence integrity mechanisms, plus a protocol for shared secret establishment. A novel aspect of this work is the protection of subscriber traffic in support of the overall communication availability security goal.