Si102x/3x
14. Advanced Encryption Standard (AES) Peripheral
The Si102x/3x devices include a hardware implementation of the Advanced Encryption Standard Block
Cipher as specified in NIST publication FIPS 197 “Advanced Encryption Standard (AES), November 2001.
The Rijndael encryption algorithm was chosen by NIST for the AES block cipher. The AES block cipher
can be used to encrypt data for wireless communications. Data can be encrypted before transmission and
decrypted upon reception. This provides security for private networks.
The AES block cipher is a Symmetric key encryption algorithm. Symmetric Key encryption relies on secret
keys that are known by both the sender and receiver. The decryption key may be obtained using a simple
transformation of the encryption key. AES is not a public key encryption algorithm.
The AES block Cipher uses a fixed 16 byte block size. So data less than 16 bytes must be padded with
zeros to fill the entire block. Wireless data must be padded and transmitted in 16-byte blocks. The entire
16-byte block must be transmitted to successfully decrypt the information.
The AES engine supports key lengths of 128-bits, 192-bits, or 256-bits. A key size of 128-bits is sufficient
to protect the confidentiality of classified secret information. The Advanced Encryption Standard was
designed to be secure for at least 20 to 30 years. The 128-bit key provides fastest encryption. The 192-bit
and 256-bit key lengths may be used to protect highly sensitive classified top secret information.
Since symmetric key encryption relies on secret keys, the security of the data can only be protected if the
key remains secret. If the encryption key is stored in flash memory, then the entire flash should be locked
to ensure the encryption key cannot be discovered. (See flash security.)
The basic AES block cipher is implemented in hardware. This hardware accelerator provides performance
that may be 1000 times faster than a software implementation. The higher performance translates to a
power savings for low-power wireless applications.
The AES block cipher, or block cipher modes based on the AES block cipher, is used in many wireless
standards. These include several IEEE standards in the wireless PAN (802.15) and wireless LAN (802.11)
working groups.
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