Browse Prior Art Database

APC025 PROPER CODE DETECT USING LOW SPEED DATA

IP.com Disclosure Number: IPCOM000007651D
Original Publication Date: 1996-May-01
Included in the Prior Art Database: 2002-Apr-11
Document File: 1 page(s) / 60K

Publishing Venue

Motorola

Related People

Ferdie Brillantes: AUTHOR [+2]

Abstract

Encryption is used to protect information in sys- tems where sensitive audio is transmitted over the air. In order for the receiving radio to successfully decrypt an encrypted transmission, the receiving radio must have the algorithm and the key that was used in the encryption process. The APC025 Com- mon Air Interface provides an ALGID (Algorithm ID) Field and a KID (Key Identifier) Field to indentily the algorithm and the key that was used to encrypt the transmitted signal, Ifthe receiving radio has the matching KID and ALGID, the received audio is decrypted and routed to the speaker. The problem with this approach is that a matching KID and ALGID does not guarantee that the correct key will be used to decrypt the audio signal. It merely indi- cates that the KID and ALGID matches. The actual key data associated with the KEYID may be differ- ent (e.g. transmitting radio maps KID = 1 to the key Ox012356789ABDEF but receiving radio maps KID = 1 to the key OxABCDEFO123456789). There- fore an attempt to decrypt the audio signal will result in noise being routed to the speaker.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 64% of the total text.

Page 1 of 1

M-ROLA Technical Developments

APC025 PROPER CODE DETECT US&G

LOW SPEED DATA

by Ferdie Brillantes and Esteban Yepez Ill

1 .O INTRODUCTION

2.0 THE PRIOR ART

  Encryption is used to protect information in sys- tems where sensitive audio is transmitted over the air. In order for the receiving radio to successfully decrypt an encrypted transmission, the receiving radio must have the algorithm and the key that was used in the encryption process. The APC025 Com- mon Air Interface provides an ALGID (Algorithm ID) Field and a KID (Key Identifier) Field to indentily the algorithm and the key that was used to encrypt the transmitted signal, Ifthe receiving radio has the matching KID and ALGID, the received audio is decrypted and routed to the speaker. The problem with this approach is that a matching KID and ALGID does not guarantee that the correct key will be used to decrypt the audio signal. It merely indi- cates that the KID and ALGID matches. The actual key data associated with the KEYID may be differ- ent (e.g. transmitting radio maps KID = 1 to the key Ox012356789ABDEF but receiving radio maps KID = 1 to the key OxABCDEFO123456789). There- fore an attempt to decrypt the audio signal will result in noise being routed to the speaker.

  In Advance Securenet (ASN) systems, a tech- nique, Proper Code Detect, was utilized to deter- mine if the correct Key was used to decrypt the received signal. This technique measured the degree of correlation ofthe decrypted signal. The audi...