Advanced Encryption Standard

By | March 14, 2012

Advanced Encryption Standard, a symmetric 128-bitblock data encryption technique developed by Belgian cryptographers Joan Daemen and Vincent Rijmen. The Advanced Encryption Standard (AES) is an encryption algorithm for securing sensitive but unclassified material by U.S. Government agencies and, as a likely consequence may eventually become the de facto encryption standard for commercial transactions in the private sector. AES is also known as Rijndael.

AES was announced by National Institute of Standards and Technology (NIST) as U.S. FIPS PUB 197 (FIPS 197) on November 26, 2001, after a 5-year standardization process in which fifteen competing designs were presented and evaluated before Rijndael was selected as the most suitable. It became effective as a Federal government standard on May 26, 2002, after approval by the Secretary of Commerce. It is available in many different encryption packages. AES is the first publicly accessible and open cipher approved by the NSA for top secret information.

Advanced Encryption Standard is the NIST’s replacement for the Data Encryption Standard (DES). The standard comprises three block ciphers, AES-128, AES-192, and AES-256, adopted from a larger collection originally published as Rijndael. Each AES cipher has a 128-bit block size, with key sizes of 128, 192 and 256 bits, respectively. The AES ciphers have been analyzed extensively and are now used worldwide, as was the case with its predecessor, the Data Encryption Standard (DES).

Advanced Encryption Standard by Joan Daemen and Vincent Rijmen


In January of 1997, The National Institute of Standards and Technology (NIST), a unit of the U.S. Commerce Department, started with a process to find a more robust replacement for the Data Encryption Standard (DES) and to a lesser degree Triple DES. The specification called for a symmetric using block encryption of 128 bits in size, supporting key sizes of 128, 192 and 256 bits, as a minimum. The algorithm was to be easy to implement in hardware and software, as well as in restricted environments and offer good defenses against various attack techniques. The algorithm was required to be work properly for next 30 plus years.

In 1998, the NIST selected 15 candidates for the AES, which was then subject to preliminary analysis by the world cryptographic community, including the National Security Agency. On the basis of this, 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 such measures as encryption and decryption speeds, key and algorithm set-up time and resistance to various attacks, both in hardware and software-centric systems. on October 2, 2000, NIST announced that Rijndael had been selected as the proposed standard. On December 6, 2001, the Secretary of Commerce officially approved Federal Information Processing Standard (FIPS) 197, which specifies that all sensitive, unclassified documents will use Rijndael as the Advanced Encryption Standard.

Data encryption is showing up in tape libraries, disk drives, and backup software, but the technology is hindered by the lack of a single standard for managing encryption keys.

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