The Advanced Encryption Standard
or AES is a symmetric block cipher used by the U.S. government to protect
classified information and is implemented in software and hardware throughout
the world to encrypt sensitive data.
The origins of AES date back to 1997
when the National Institute of Standards and Technology (NIST) announced that
it needed a successor to the aging Data Encryption Standard (DES) which was
becoming vulnerable to brute-force attacks.
This new encryption algorithm
would be unclassified and had to be "capable of protecting sensitive
government information well into the next century." It was to be easy to
implement in hardware and software, as well as in restricted environments (for
example, in a smart card) and offer good defenses against various attack
techniques.
Choosing AES
The selection process to find
this new encryption algorithm was fully open to public scrutiny and comment; this
ensured a thorough, transparent analysis of the designs. Fifteen competing
designs were subject to preliminary analysis by the world cryptographic
community, including the National Security Agency (NSA). In August 1999, NIST
selected five algorithms for more extensive analysis. These were:
MARS, submitted by a large team from IBM
Research
RC6, submitted by RSA Security
Rijndael, submitted by two Belgian
cryptographers, Joan Daemen and Vincent Rijmen
Serpent, submitted by Ross Andersen, Eli
Biham and Lars Knudsen
Twofish, submitted by a large team of
researchers including Counterpane's respected cryptographer, Bruce Schneier
Implementations of all of the
above were tested extensively in ANSI, C and Java languages for speed and
reliability in encryption and decryption, key and algorithm setup time, and
resistance to various attacks, both in hardware- and software-centric systems. Members
of the global cryptographic community conducted detailed analyses (including
some teams that tried to break their own submissions).
After much enthusiastic feedback,
debate and analysis, the Rijndael cipher -- a mash of the Belgian creators' last
names Daemen and Rijmen -- was selected as the proposed algorithm for AES in
October 2000 and was published by NIST as U.S. FIPS PUB 197. The Advanced
Encryption Standard became effective as a federal government standard in 2002. It
is also included in the ISO/IEC 18033-3 standard which specifies block ciphers
for the purpose of data confidentiality.
In June 2003, the U.S. government
announced that AES could be used to protect classified information, and it soon
became the default encryption algorithm for protecting classified information
as well as the first publicly accessible and open cipher approved by the NSA
for top-secret information. AES is one of the Suite B cryptographic algorithms
used by NSA's Information Assurance Directorate in technology approved for
protecting national security systems.
Its successful use by the U.S. government
led to widespread use in the private sector, leading AES to become the most
popular algorithm used in symmetric key cryptography. The transparent selection
process helped create a high level of confidence in AES among security and
cryptography experts. AES is more secure than its predecessors -- DES and 3DES --
as the algorithm is stronger and uses longer key lengths. It also enables
faster encryption than DES and 3DES, making it ideal for software applications,
firmware and hardware that require either low-latency or high throughput, such
as firewalls and routers. It is used in many protocols such as SSL/TLS and can
be found in most modern applications and devices that need encryption
functionality.
How AES encryption works
