Operating Manual

10-2 5100 ES Models II/III Portable Radio Operating Manual March 2008
Secure Communication (Encryption)
10.1.2 AES (Advanced Encryption Standard)
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. AES encryption,
like DES encryption, is an optional radio feature that must be purchased and then enabled
at the factory.
10.1.3 Encryption Available With Various Channel Types
Analog Channels - On analog conventional and SMARTNET/SmartZone channels, DES
encryption provides secure communication.
Digital Channels - On conventional P25, SMARTNET/Smart Zone, and P25 Trunking
channels, the DES-OFB or AES-OFB protocol is used.
10.1.4 FIPS Modes
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.
10.2 Encryption Keys
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.
When an encrypted message is transmitted, the encryption Algorithm ID (ALID) and key
ID (KID) are usually included in the message. This tells the receiving radio which key and
algorithm must be used to decrypt the message.