Analysis of Handover Key Management schemes under IETF perspective

Abstract

The Extensible Authentication Protocol (EAP) has been standardized within the Internet Engineering Task Force (IETF) in order to provide flexible mechanisms for authentication and key management for network access control. However, some deficiencies have been revealed and recognized as a major obstacle to achieving secure and seamless handover in mobile scenarios. HOKEY (Handover Keying) Working Group in IETF is standardizing low-latency EAP re-authentication and key distribution protocols to address these deficiencies. This paper provides a critical analysis of the on-going work.

Introduction

Faced with increasing user demand for new communication and network services, telecommunication operators are providing network access through different access technologies. Additionally, the operators need to manage and control subscribers, independently of access technologies. This has usually been achieved through authenticated network access with the support of Authentication, Authorization and Accounting (AAA) infrastructures [1]. Furthermore, thanks to the deployment of these infrastructures, it has been possible to establish roaming agreements which allow mobile subscribers to access the network services in different administrative domains, including the home domain where the users have their subscription and visited domains that have roaming relationships with the home domain.

In order to provide a flexible way to carry out the authentication process required for network access, the standardization body Internet Engineering Task Force (IETF) has designed the Extensible Authentication Protocol (EAP) [2], which allows different authentication mechanisms through the so-called EAP methods. Additionally, the protocol has been conceived to be technology independent and to allow an easy integration in deployed AAA infrastructures [3]. These features have promoted its use in different wireless technologies such as IEEE 802.11 [4] or IEEE 802.16e [5] and different protocols used for network access authentication (e.g. PANA [6], IKEv2 [7]).

However, EAP has shown some drawbacks when mobility is taken into consideration. In particular, EAP authentication is usually a time-consuming process [8], [9] and it usually takes place each time the mobile moves to a new EAP authenticator, regardless of whether the mobile has been previously authenticated or owns unexpired keying material. Additionally, EAP messages are exchanged between the mobile in the visited domain and the EAP server in the home domain. These two issues, which have generally been called the handover keying problem, are known to be major contributors to the handover latency that negatively affects session continuity during handover.

To solve these problems, the Handover Keying Working Group (HOKEY WG) has been designated within the IETF, to produce a collection of solutions that reduce the latency introduced during an EAP authentication. In this paper, we survey and analyze the work in progress in HOKEY WG, mainly from a security standpoint. From the analysis, we also provide possible solutions and alternatives to solve different problems found in the current specifications.

The remainder of the paper is organized as follows: in Section 2 we analyze EAP, since it is the basis for understanding the problem space associated to handover keying. Additionally, we describe the problems that HOKEY WG is trying to solve. Section 3 describes the different documents submitted and currently discussed within the group. In Section 4, we make a critical analysis of some issues found in the HOKEY WG documents and propose possible alternatives. Finally, Section 5 summarizes the related work, and in Section 6, we outline some conclusions and future lines.