|Designers||Vincent Rijmen and Paulo S. L. M. Barreto|
|Key sizes||128 bits|
|Block sizes||64 bits|
|Best public cryptanalysis|
|No attack better than on the first five rounds is known.|
In cryptography, KHAZAD // is a block cipher designed by Paulo S. L. M. Barreto together with Vincent Rijmen, one of the designers of the Advanced Encryption Standard (Rijndael). KHAZAD is named after Khazad-dûm, the fictional dwarven realm in the writings of J. R. R. Tolkien (see also Khazad). KHAZAD was presented at the first NESSIE workshop in 2000, and, after some small changes, was selected as a finalist in the project.
KHAZAD has an eight-round substitution-permutation network structure similar to that of SHARK, a forerunner to Rijndael. The design is classed as a "legacy-level" algorithm, with a 64-bit block size (in common with older ciphers such as DES and IDEA) and a 128-bit key. KHAZAD makes heavy use of involutions as subcomponents; this minimises the difference between the algorithms for encryption and decryption.
The authors have stated that, "KHAZAD is not (and will never be) patented. It may be used free of charge for any purpose."
Frédéric Muller has discovered an attack which can break five of KHAZAD's eight rounds. No attacks better than this are known as of August 2009.
- P. Barreto, V. Rijmen (13–14 November 2000). The Khazad legacy-level block cipher. First open NESSIE Workshop. Leuven. p. 15. Retrieved 2013-01-14.
- Alex Biryukov (February 2003). Analysis of Involutional Ciphers: Khazad And Anubis (PDF/POSTSCRIPT). 10th International Workshop on Fast Software Encryption (FSE '03). Lund: Springer-Verlag. pp. 45–53. Retrieved 2013-01-14.
- Frédéric Muller (December 2003). A New Attack against Khazad. Advances in Cryptology - ASIACRYPT 2003. Taipei: Springer-Verlag. pp. 347–358. Retrieved 2013-01-14.
- Paulo S. L. M. Barreto (2008-11-19). "The KHAZAD Block Cipher".