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Browse Prior Art Database

DISPATCHER CONTROLLED SECURE CALL

IP.com Disclosure Number: IPCOM000006719D
Original Publication Date: 1992-Dec-01
Included in the Prior Art Database: 2002-Jan-25
Document File: 2 page(s) / 133K

Publishing Venue

Motorola

Related People

Rolf Salomon: AUTHOR [+3]

Abstract

In trunked radio control systems management dis- patchers may regroup one or more radios to dynamic T&groups or Subfleets to allow communication between radio operators that would not normally belong to the pre-coded groups available on the selectors on the radio units, as need arises. This feature is utilized to coordi- nate activities of subscriber groups that would not nor- mdly have a need to communicate, for instance police car fleets in neighboring counties. Upon acknowledging a Regroup command, a radio unit will ignore the cur- rent setting of its Talkgroup Selector and move to the Talkgroup specified in the command (the Target Talkgroup).

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m MO-LA INC.' Technical Developments Volume 17 December 1992

DISPATCHER CONTROLLED SECURE CALL

by Rolf Salomon, Ory Biran, and David Bar-On

INTRODUCTION

  In trunked radio control systems management dis- patchers may regroup one or more radios to dynamic T&groups or Subfleets to allow communication between radio operators that would not normally belong to the pre-coded groups available on the selectors on the radio units, as need arises. This feature is utilized to coordi- nate activities of subscriber groups that would not nor- mdly have a need to communicate, for instance police car fleets in neighboring counties. Upon acknowledging a Regroup command, a radio unit will ignore the cur- rent setting of its Talkgroup Selector and move to the Talkgroup specified in the command (the Target

Talkgroup).

  Radio units may be equipped with encryption mod- ules, which enable the radio operators to communicate in a s-bled code (Secure Calls) by digitizing the voice input and subsequently submit it to an encryption algo- rithm. Only radio operators whose radios are loaded with the same encryption key may communicate encrypted ("in secure mode"). Furthermore, the encryption algorithm is designed to produce an output with a spectral distribution approaching white noise, fore- most to make it hard to break the code, but also to hide the fact that a conversation is taking place at all. The encryption feature is activated by the radio operators by use of a switch on the radio unit, to toggle between "secure" and "clear" communication. No means exist for dispatchers to remote-activate encryption in radio units.

  Secure conversation is used for protecting business information, and for protecting sensitive information as part of overall security strategies for police (undercover) work.

PROBLEM

  In emergency situations that require Secure com- munication, radio operators may be regrouped to ena- ble them to communicate, as outlined in the introduction.

  As radio operators are regrouped, they will decide whether to switch to secure communication either by pre-arranged procedures or by agreement reached by discussion on the air. A security hazard exists ifthe dis- cussion on whether to switch to secure communication is held in "clear" mode, or a radio user fails to realize that his/her radio has been regrouped and subsequently initiates a "clear" call.

  The suggested invention is to enable a dispatcher to control whether the state or radios being regrouped is to be "clear" or "secure?

DESCRlPTlON OFTHE INVENTION

  When issuing a Regroup command, a dispatcher will be able to specify the Regrouped radios to change to Secure (encrypted) communication. Upon acknowl- edging a Regroup command specifying Secure commu- nication, a radio will move to the Target Talkgroup, and enter Secure mode, ignoring the cum-m setting of fhe Secure switch on the radio.

  To ensure a high level or secrecy, the Regroup com- mand specifying Secure communication will not specify an encrypt...