Rijndael's design bases on the so called ``wide trail'' strategy, invented by Joan Daemen, and described, e.g., in his ``Cipher and hash function design. Strategies based on linear and differential cryptanalysis.'' (available from his homepage). The wide trail strategy offers protection against the conventional linear and differential cryptanalysis methods, and was employed by Daemen and Vincent Rijmen in block cipher Square.

Square is an eight-round SPN (substitution-permutation network) cipher with 128-bit key length and 128-bit block length. Rijndael is very similar to Square. The most easily spotted changes are: (1) higher flexibility (support for a multitude of key and block lengths), and (2) increased number of rounds, to offer additional security, although also Square remains unbroken to this moment.

Rijndael was announced to be the new AES by NIST in October 2000. The official FIPS will be ready in summer 2001.

The process of choosing the AES took a few years. None of the final candidates was broken at the time of choice. Rijndael was chosen due to its simple and elegant design, flexibility, and speed in most of the software and hardware platforms.

In their choice, NIST carefully considered the opinion of academia, who were largely in favor of Rijndael. NIST announcement was greeted with an approval from leading cryptographers.

The essential URLs:

  1. The block cipher Rijndael, official homepage by the authors. http://www.esat.kuleuven.ac.be/~rijmen/rijndael/
  2. Joan Daemen, homepage. ttp://www.esat.kuleuven.ac.be/~rijmen/daemen/
  3. Vincent Rijmen, homepage. http://www.esat.kuleuven.ac.be/~rijmen/
  4. The block cipher Square, official homepage by the authors. http://www.esat.kuleuven.ac.be/~rijmen/rijndael/
  5. AES homepage, http://www.nist.gov/aes/
  6. AES Candidates: A Survey of Implementations, http://www.tml.hut.fi/~helger/aes/