Browse Prior Art Database

SECURE RECONFIGURATION OF ENCRYPTION ALGORITHMS IN A HARDWARE DEVICE

IP.com Disclosure Number: IPCOM000008323D
Original Publication Date: 1997-Sep-01
Included in the Prior Art Database: 2002-Jun-05
Document File: 3 page(s) / 139K

Publishing Venue

Motorola

Related People

Jason Livermore: AUTHOR [+2]

Abstract

Motorola radios that use hardware encryption devices cannot be reprogrammed to accept another algorithm once they are installed and programmed in the factory. The hardware devices used are custom and costly masked parts. To provide multi-algorithm capability and reduced cost for encryption-capable radios, a method that uses reprogrammable, low-cost devices must be sought out. One such method, described in this paper, employs the use of programmable logic arrays.

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MO7VROLA Technical Developments

SECURE RECONFIGURATION OF ENCRYPTION ALGORITHMS IN A HARDWARE DEVICE

by Jason Livermore and Dean Vogler

ABSTRACT

  Motorola radios that use hardware encryption devices cannot be reprogrammed to accept another algorithm once they are installed and programmed in the factory. The hardware devices used are custom and costly masked parts. To provide multi-algorithm capability and reduced cost for encryption-capable radios, a method that uses reprogrammable, low-cost devices must be sought out. One such method, described in this paper, employs the use of programmable logic arrays.

INTRODUCTION

  Motorola offers a range of 2-way encryption- capable radios in several different algorithms. The term algorithm refers to the type of encryption used. For example, the widely used Data Encryption Standard (DES) is an example of a published encryption algorithm used in Motorola products and in many other applications world-wide. Though DES is a published algorithm, meaning that the algorithm's description is available to the public, there are other encryption algorithms for which the inner-workings are proprietary. In Motorola, radios that use such proprietary algorithms use hardware devices that contain the algorithm in a masked part, making intrusion very difficult. However, this approach imposes certain limitations. In a multi- crypt0 envrronment, where more than one different encryption algorithm may be used, the solution is to add one or more masked hardware devices to the encryption module, albeit at much higher cost.

  A better solution would be to eliminate the use of high cost specialized parts and use lower cost generic devices that could be reprogrammed to the desired algorithm. The method employed must take into account the issues of protecting the proprietary encryption algorithm at all times. The invention described below provides a mechanism to configure

a programmable logic array, used to perform a particular encryption algorithm, in a way that keeps the algorithm from being discovered.

DESCRIPTION OF INVENTION

  The invention revolves around the use of two programmable logic arrays. One is designated the Fusemap Decryption PLA (FDP), and the other is the Programmable Algorithm PLA (PAP). There is in addition to the PLA's a host processor. Implementation of FlashPort capability, in terms of offering encryption algorithms as an aftermarket option, was considered in the design.

  The invention provides for the transfer of any of several available fusemaps, or bitstreams, from internal (host processor) or external (FlashPort device) memory into the Programmable Algorithm PLA by using the Fusemap Decryption PLA to decrypt the bitstream just before it goes into the PAP.

  The fusemaps must have been previously encrypted with a fixed key unknown to the user. The factory will initially seed the Fusemap Decryption PLA with a fixed key and algorithm. The type of algorithm that is used by the FDP, and likewise the en...