E F Johnson Company 2425M80 Benutzerhandbuch

Draft 02 - Sep 1 2015

7-3

An encryption key is a cryptographic variable that is required by the encryption algorithm 
to encrypt and decrypt voice or data. To maintain system security, these keys must be 
protected from disclosure and also periodically replaced or updated.

With the AES and DES hardware encryption and ARC4 software encryption used by 
EFJohnson Technologies radios (see Section 7.1), the same encryption key is used by both 
the encrypting (sending) and decrypting (receiving) radio. AES encryption keys are 
generated from a string of 64 hexadecimal characters, and DES keys are generated from a 
string of 16 hexadecimal characters. Another four hexadecimal characters are used to 
specify the key ID. Multiple keys can be loaded into a radio using OTAR or manual 
loading. ARC4 software encryption keys are generated from a string of 10 hexadecimal 
characters. Multiple keys can be loaded into a radio using Armada.

If an attempt is made to transmit a secure message without loading the corresponding key, 
“KEYFAIL” is displayed. The message must then be transmitted in the clear mode (this is 
possible only if the channel is strapped to “switchable”) or the key must be loaded.

Each encryption key is programmed with a Key ID (also called Logical ID). This ID plus 
the algorithm ID (ALGID) is transmitted in the message on digital channels. The radio 
receiving the message must have a key with the same IDs in order to decrypt it.