OTAR
(Over-The Air-Rekeying) is the function to overwrite an Encryption Key for P25 encryption by radio. Using this
function, the Encryption Key can be updated without using the Key Loader by remote operation.
OTAR realizes the function by transmitting and receiving an OTAR message called Key Management Message (KMM) in
CAI Data Packets which comply with the P25 standards. (Refer to
.)
The Encryption Key is managed by the Key Manager function of the Key Management Facility (KMF) which is a component
of the system.
KMF
System
Figure 5-1 Key Manager
Note
OTAR cannot be used for the Encryption function by means of DES (Built-in DES).
5.1
About the Encryption Key
The following are 2 types of Encryption Keys which are used for OTAR:
Traffic Encryption Key
The Traffic Encryption Key (TEK) is used for voice and data communications. The transceiver must have at least one TEK.
The TEK is the Encryption Key which is used other than for OTAR.
Key Encryption Key
Key Encryption Key (KEK) is used for encrypting an Encryption Key which is included in the KMM. To use OTAR, the
transceiver must have at least one KEK. The KEK is the Encryption Key which is used for OTAR only. The KEK is configured
from CKR No. 61440 to 65535 (from F000 to FFFF) and can be distinguished from the TEK.
The KEK unique to the transceiver is called UKEK (Unique KEK), and the KEK common to a group is called CKEK (Common
KEK).
Note
0
The SCM retains the Key Names different from the Key Names which are configured in the Multi-key List of KPG-D1/
D1N. The Key Name retained by the SCM supports a maximum of 31 characters.
0
Multi-key List is the list to configure the CKR No. of Encryption Keys. The CKR No. corresponds to the CKR ID in the
Multi-key List of KPG-D1/ D1N.
5 P25 OTAR
5
P25 OTAR
P25 FUNC (K)/Ver 2.20
181