Browse Prior Art Database

COMPARATOR WITH ENCRYPTION SYNCHRONIZATION STORAGE

IP.com Disclosure Number: IPCOM000008432D
Original Publication Date: 1997-Dec-01
Included in the Prior Art Database: 2002-Jun-13
Document File: 1 page(s) / 52K

Publishing Venue

Motorola

Related People

John Kochanek: AUTHOR [+3]

Abstract

In a secure digital voting system, there can be subscriber and console audio present at the same time. Only one of two sources will be repeated, whichever is configured in the comparator to have higher priority. If the higher priority signal ends while the lower priority signal is still present, the comparator resumes to the latter. This means that subscribers receiving the call will hear the end of one call and then start hearing the middle of the lower-priority call. In current systems, the encryption module for the subscriber is unable to start decrypting properly until it receives encryption synchronization (ESYNC), which for example only gets put out every 360 ms in APCO-25 CAI. The user could experience an unacceptable amount of truncation in the form of silence or improperly decrypted audio. For protocols with longer times between synchronization, this becomes even more of a problem.

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MOTOROLA Technical Developments

COMPARATOR WITH ENCRYPTION SYNCHRONIZATION STORAGE

by John Kochanek, Joel Klein and Boris Dubinsky

PROBLEM

  In a secure digital voting system, there can be subscriber and console audio present at the same time. Only one of two sources will be repeated, whichever is configured in the comparator to have higher priority. If the higher priority signal ends while the lower priority signal is still present, the comparator resumes to the latter. This means that subscribers receiving the call will hear the end of one call and then start hearing the middle of the lower-priority call. In current systems, the encryption module for the subscriber is unable to start decrypting properly until it receives encryption synchronization (ESYNC), which for example only gets put out every 360 ms in APCO-25 CAI. The

user could experience an unacceptable amount of truncation in the form of silence or improperly decrypted audio. For protocols with longer times between synchronization, this becomes even more of a problem.

SOLUTION

  As the comparator takes in a lower priority signal that is blocked from being routed, it will store the encryption synchronization information. If the comparator ever needs to resume to that signal, it will first send a header frame that includes the syn- chronization information. Thus the subscriber can immediately begin decrypting the following audio.

High Priority

Signal

Low Priority Signal

HI HI HI HI HI HI HI HI H

LO LO LO...