Browse Prior Art Database

OPTIMAL CIPHER KEY MANAGEMENT IMPLEMENTATION FOR TRUNKED DIGITAL RADIO SYSTEMS

IP.com Disclosure Number: IPCOM000009774D
Original Publication Date: 2000-May-01
Included in the Prior Art Database: 2002-Sep-18
Document File: 4 page(s) / 189K

Publishing Venue

Motorola

Related People

Jason Johur: AUTHOR

Abstract

Multiple priority levels and persistence periods are associated with cipher key material stored and disseminated within a digital mobile radio system employing air interface encryption, to provide an optimal key management implementation.

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This is the abbreviated version, containing approximately 34% of the total text.

MOTOROLA

Technical Developments

OPTIMAL CIPHER KEY MANAGEMENT IMPLEMENTATION FOR TRUNKED DIGITAL RADIO SYSTEMS

by Jason Johur

ABSTRACT

Multiple priority levels and persistence periods are associated with cipher key material stored and disseminated within a digital mobile radio system employing air interface encryption, to provide an optimal key management implementation.

INTRODUCTION

This paper describes an optimal key management implementation designed for trunked digital radio systems employing air interface encryption service and mixed mobile station capabilities.

PROBLEMS TO BE SOLVED

Digital mobile radio systems with air interface encryption may be designed to meet the requirements of the public safety market. In these systems there is a need to protect the identity and signaling information of a mobile station during cell re-selection. In many cases this is difficult, due to the mixed capabilities of the infrastructure and the mobile stations, and the limited resources of the system.

GSM is a digital mobile radio system that employs air interface encryption. However, GSM does not meet many of the needs of the public safety market due to its simplicity. Also, and more importantly, GSM does not allow for the same diversity in capabilities offered by the mobile station and the infrastructure.

PROPOSEDSOLUT1ON TO THE PROBLEMS

The idea of this paper embodies the principles of multiple priority levels and persistence periods associated with cipher key material stored and disseminated within a digital mobile radio system

Motorola, Inc. 2000

employing air interface encryption, to provide an optimal key management implementation.

When a mobile station moves from one cell to another within a system (roaming), the mobile station has to perform certain cell re-selection procedures. The exact nature of the procedure will depend on the capabilities of the mobile station and the infrastructure. Generally, three forms of cell reselection may be employed:

. Cell re-selection with preferred neighbor cell selected and forward registration (sometimes referred to as seamless handover),

. Cell re-selection with preferred neighbor cell selected and no forward registration,

. Cell re-selection with no preferred neighbor cell selected and no forward registration.

In order to minimize exposure of control and traffic information over the air interface, the infrastructure must use an optimal key management strategy to ensure cipher key material is available to the base sites of the infrastructure during a cell change. However, it is not practicable on cost and performance grounds to store cipher key material in every base station within the infrastructure.

For a mobile station that is not capable of indicating a preferred neighbor cell, the mobile station may indicate to the infrastructure that it is invoking cell res election procedures that do not involve a preferred neighbor cell. On reception of such signaling by the infrastructure, the infrastructure will tra...