What is the Rijndael Algorithm?

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  • Written By: Mary Elizabeth
  • Edited By: Bronwyn Harris
  • Last Modified Date: 12 October 2019
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In the world of computer security, an algorithm refers to a cryptographic algorithm, a set of rules and/or procedures for encrypting messages. Some algorithms are more complex than others, and hence, harder to crack. The Rijndael algorithm is one such algorithm, and is very important in global communications on a number of fronts.

The term Rijndael — which some pronounce as /RAIN dahl/ and others pronounce as /RINE dahl/ — was formed by joining the beginnings of the last names of the two developers, Belgian cryptographers Joan Daemen and Vincent Rijmen. The Rijndael algorithm was created in response to an invitation issued by NIST, the National Institute of Standards and Technology, in 1997 for cryptographers to submit an advanced algorithm to form the basis of AES, the Advanced Encryption Standard. The Rijndael algorithm was one of 21 submissions by teams from 11 countries, and it was the one selected in 2000, with the result that AES is sometimes called “AES (Rijndael).”

Rijmen and Daemen developed the Rijndael algorithm from Square, an algorithm they had collaborated on earlier. The Rijndael algorithm is a block cipher, an alternative to a stream cipher. The data is processed in 128 bit blocks, and keys may be 156 bits, 192 bits, or 256 bits.


The purpose of AES was to replace DES, the Data Encryption Standard, as a more secure substitute. The United States government chose AES, first for sensitive, but unclassified, documents in 2000, and in 2003, the NSA (National Security Agency) approved using higher bit keys — only 192 bits and 256 bits — for top secret documents. The New European Schemes for Signatures, Integrity, and Encryption (NESSIE) consortium adopted AES in 2003 as well.

AES is used in IKE (Internet Key Exchange), which transmits the secret key for decryption using public key cryptography, and in IPSec (Internet Protocol Security). Some security experts feel that the Rijndael algorithm was not the best-suited algorithm for the kind of uses to which AES is put. Others claim that none of the algorithms would have earned universal support. Attempts to break it are ongoing, and bets have been placed on how long it will be before it is cracked.


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