Browse Prior Art Database

OTAR MULTIPLEXED KEY ENCRYPTION KEY

IP.com Disclosure Number: IPCOM000007438D
Original Publication Date: 1995-Jul-01
Included in the Prior Art Database: 2002-Mar-26
Document File: 1 page(s) / 52K

Publishing Venue

Motorola

Related People

Hans Christopher Sowa: AUTHOR

Abstract

The system is conventional Over-The-Air- Rekeying (OTAR) or is trunking OTAR. Radios with encryption may request encryption keys from a Key Management Controller (KMC) by a menu selec- tion that activates a Rekey Request. A Rekey Request data message (includes the radio's ID) is sent from the radio to the KMC so the radio can be OTARed the encryption keys that it would use for voice. OTAR messages from the KMC, sending encryption keys to the radio are encrypted using the key encryption key (KEK) ofthe radio.

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MOlVROLA Technical Developments

8

OTAR MULTIPLEXED KEY ENCRYPTION KEY

by Hans Christopher Sowa

SYSTEM BACKGROUND:

  The system is conventional Over-The-Air- Rekeying (OTAR) or is trunking OTAR. Radios with encryption may request encryption keys from a Key Management Controller (KMC) by a menu selec- tion that activates a Rekey Request. A Rekey Request data message (includes the radio's ID) is sent from the radio to the KMC so the radio can be OTARed the encryption keys that it would use for voice. OTAR messages from the KMC, sending encryption keys to the radio are encrypted using the key encryption key (KEK) ofthe radio.

THE PROBLEM:

  A mobile radio in a car is used by different users, perhaps when shiRs change or for special assign- ments. Ifthe radio users require different encryption keys, they cannot use a Rekey Request since it can only get one set of encryption keys. The basic prob- lem is that the encryption keys are tied to the radio

hardware (via the KEK), and are not tied to the users ofthe radio.

THE SOLUTION:

  The KMC needs to allow more than one set of encryption keys to be tied to a KEK. The set of encryption keys OTARed would be based on the user requesting the encryption keys. This effectively multiplexes the KEK ofa radio over several users.

  The radio would send a Rekey Request that would also include the user's identification and perhaps a password to validate the user. The KMC would deter- mine if that user was authorized to use that radio, and if...