AES, short for Advanced Encryption Standard, is a widely adopted symmetric encryption scheme used, for instance, to secure electronic communication and messages. AES – as its name implies - has been the outcome of standardization and evaluation process which took years to select from the best encryption algorithms. Finally, in 2001, the Rijndael algorithm has been chosen as winner by the US National Institute of Standards and Technology (NIST) to be implemented as underlying security algorithm of the AES standard which as of the these days has largely replaced its predecessor and derivates of DES (Data Encryption Standard) which is longer considered secure due to its small 56-bit key length for example.
The Rijndael algorithm, invented by two cryptographers Vincent Rijmen and Joan Daemen, implements the mathematical operations substitution, transposition, as well as permutation to plaintext, the term used to describe input in the cryptography domain. The AES Advanced Encryption Standard uses 10 rounds of these algebraic operations in a complex scheme to produce encrypted output, or cipher text as it is called in expert terms. AES-192 and AES-256 have 12 and 14 rounds, respectively.
In the AES implementation of Rijndael the algorithm operates on 128 bits block ciphers, and comprises key lengths of 128, 192 and 256 bits. It is common to refer to the symmetric key AES encryption standard as AES-128, AES-192 and AES-256 depending on the key strength. More about encryption can also be found in Bright Hub’s article Types of Encryption which explains the difference between asymmetric and symmetric encryption also shedding a light on stream and block ciphers.
Whereas cryptography aims at securing plain text does cryptanalysis try to break the key or underlying algorithm of an encryption scheme, Rijndael in the case of AES here. Cracking a 256-bit key is computationally infeasible but cryptanalysts who are aware of the inner working of Rijndael and who apply much more sophisticated methods than brute-force believe that the security margin is narrowing. Check out our article Can AES Encryption be Cracked? which takes into account the latest news about the security or strength of AES.
If you find this article about AES interesting you may also be interested in Bright Hub’ article about Bruce Schneier’s Blowfish and Twofish algorithms.