Advance Encryption Standard

Advance Encryption Standard (AES) is a encryption algorithm which overcomes limitations of DES or Triple DES.

As DES have -

• Theoretical attacks that can break it.
• Demonstrated exhaustive key search attacks.

In order to overcome this we can use Triple-DES (3DES), but it is slow as it has small data blocks.

US NIST issued call for ciphers in 1997, 15 candidates accepted in Jun 98. Out of which 5 were shortlisted in Aug-99. 

Rijndael was selected as the AES in Oct-2000 issued as FIPS PUB 197 standard in Nov-2001.

Overview:

AES cipher was designed by Rijmen-Daemen in Belgium.

It has 128/192/256 bit keys, 128 bit data. 

It is an iterative rather than Feistel cipher:

• Processes data as block of 4 columns of 4 bytes
• Operates on entire data block in every round

Designed to have:

• Resistance against known attacks
• Speed and code compactness on many CPUs
• Design simplicity