User's Manual

Date Code 20050615 Instruction Manual SEL-3022 Transceiver
Wireless Operator Interface Security
The SEL Security Application
C.11
Cryptographic Manual—Do Not Copy
might use K1 for encryption and K2 for decryption. The AES encryption algorithm the
SEL-3022 uses is a symmetric block cipher, with an encryption/decryption key size of
128 bits.
The Advanced Encryption Standard (AES) is the latest encryption standard adopted by
the National Institute of Standards and Technology (NIST). In 1997, NIST challenged
the cryptographic community to develop the next generation encryption algorithm to
replace the aging DES and 3DES encryption standards. In 2000, NIST chose the
Rijndael encryption algorithm as the AES encryption standard. During the evaluation
of candidates for the AES standard, some of the best cryptanalysts in the world
analyzed and approved Rijndael. Since NIST adopted the standard in 2001, AES has
proven to be very effective against known attacks.
Combined HMAC SHA-1
and AES Encryption Security
Every frame transmitted over the SEL-3022 wireless operator interface is authenticated
with an HMAC SHA-1 keyed hash digest and encrypted with the AES encryption
algorithm (both algorithms are described in detail in the HMAC SHA-1 Authentication
Overview and AES Overview sections above). As shown in Figure C.4, the SEL-3022
first forms the HMAC SHA-1 hash output from the original frame data payload and the
128-bit authentication key. This keyed message fingerprint is then appended to the end
of the frame data payload, and the resulting composite message is encrypted by the
AES encryption function through use of a separate, 128-bit encryption key (the
authentication key and encryption key are completely independent).
Figure C.4 SEL-3022 Security Application Overview
Upon receipt of any frame on the wireless operator interface, the SEL-3022 uses the
programmed 128-bit secret encryption/decryption key to AES decrypt the entire frame.
The SEL-3022 then uses the programmed 128-bit authentication key to calculate the
Authentication Key
Encryption Key
Final Encrypted and
Authenticated Frame
Message
Message Message
HMAC
Hash
HMAC
Hash
HMAC
Hash
HMAC
Function
AES
Encryption
Preliminary Copy