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An encryption standard called AES is replacing DES-OFB encryption on digital (P25) 
channels. It uses a 128-, 192-, or 256-bit encryption key instead of the 64-bit key used with 
DES. EFJohnson radios currently support only 256-bit AES keys. The type of encryption 
(DES or AES) is determined by the type of encryption key that is loaded (see Section 
10.2), and not by the PC Configure programming software. AES encryption, like DES 
encryption, is an optional radio feature that must be purchased and then enabled at the 
factory (or by a factory-created option file).

Analog Channels - On analog conventional and SMARTNET/SmartZone channels, DES 
encryption provides secure communication.

Digital Channels - On digital Project 25 and SMARTNET/Smart Zone channels, the 
DES-OFB or AES-OFB protocol is used.

FIPS 140-2 is a Federal Information Processing Standard for encrypted radios used by the 
Federal Government. This standard specifies Federal security requirements for 
cryptographic modules for a wide range of applications and environments. All 5300 ES 
models are FIPS certified.

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 encryption used by EFJohnson radios (see Section 10.1), 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.