E F Johnson Company 2425372 Benutzerhandbuch

Analog Channels - When this feature is disabled and a message is received with the 
wrong key, the audio unmutes and garbled (encrypted) audio is heard. However, if 
this occurs with this feature enabled, the audio remains muted.

Digital Channels - When this feature is enabled and a message is received with a 
different key, but the key resides in the radio, the audio is decrypted and received 
normally even though the key is assigned to a different talk group. If this feature is 
disabled or the key does not reside in the radio, the audio remains muted.

On conventional digital (P25) channels, the encryption strapping mode and PID are 
programmed on a per talk group basis similar to the trunked modes (SMARTNET/
SmartZone/P25 Trunked). However, with this mode only, there is the option to override 
the talk group encryption programming and program it on a per-channel basis. Therefore, 
if desired on conventional digital channels, encryption can be programmed differently for 
each channel. Conventional analog channel encryption is always programmed on a per-
channel basis.

OTAR stands for “Over-The Air-Rekeying”. This is the process of sending encryption 
keys and related key management messages over-the-air to specific radios. The advantage 
of OTAR is that it allows these keys to be quickly and conveniently updated when 
necessary. It is no longer necessary to periodically travel to the radio location or bring the 
radio into a maintenance facility to load new keys.

The actual OTAR rekeying functions are performed by a Key Management Facility 
(KMF) that sends Key Management Messages (KMM) to the radios. These messages are 
themselves encrypted using a unique key. Radios must be OTAR-compatible and 
programmed for OTAR for this type of rekeying to occur.

OTAR is available only on P25 conventional and trunked channels, and only to program 
DES-OFB and AES keys. It is not used on SMARTNET/SmartZone channels or to load 
DES keys.