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DIRECT SUBSCRIBER TO SUBSCRIBER RADIO OTAR, WITHOUT A BASE STATION OR KEY MANAGEMENT FACILITY

IP.com Disclosure Number: IPCOM000008637D
Original Publication Date: 1998-Mar-01
Included in the Prior Art Database: 2002-Jun-28
Document File: 1 page(s) / 56K

Publishing Venue

Motorola

Related People

Curtis D. Lehman: AUTHOR

Abstract

To rekey a mobile radio requires either physical contact with a key loader device or over the air rekeying (OTAR), one way being the APCO-25 OTAR protocol. Currently the APCO-25 OTAR requires a key management facility and base station.

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MOTOROLA Technical Developments

DIRECT SUBSCRIBER TO SUBSCRIBER RADIO OTAR, WITHOUT A BASE STATION OR KEY MANAGEMENT FACILITY

by Curtis D. Lehman

BACKGROUND

  To rekey a mobile radio requires either physical contact with a key loader device or over the air rekeying (OTAR), one way being the APCO-25 OTAR protocol. Currently the APCO-25 OTAR requires a key management facility and base station.

THE PROBLEM

   Whenever the base station and/or key manage- ment facility are not available, OTAR is not possible. This problem could become apparent to customers when they have had a catastrophic disaster that causes the base station to be lost. The disaster causes a greater need for communications and also a poten- tial increase in users. At such a time, any mobile radios that do not have the same keys can't commu- nicate to each other securely and can't get OTAR to work so they can communicate securely.

THE SOLUTION

  Every radio in a system would require at least one common key encryption key to the system besides the common key encryption key for there subnet; let's call it a common disaster key encryp- tion key (CDKEK). When a OTAR is needed and the system is down, the mobile radio should then issue the rekey request to all other mobile radios. The first mobile radio that responds back acknowl- edging the request will be designated as the new key management facility for this request. It will use CDKEK and the OTAR protocol to send all the traf- fic encryption keys to the r...