NOEKEON is a cipher with a block and key length of 128 bits. It was developed by Joan Daemen, Michaël Peeters, Gilles Van Assche and Vincent Rijmen and submitted to NESSIE (New European Schemes for Signatures, Integrity and Encryption) in 2000. Unfortunately NOEKEON did not get past the first stage of the contest. The block cipher finalists were AES (Advanced Encryption Standard), MISTY1, SHACAL-2 and Camellia.

However NOEKEON is comprised of two block ciphers, Direct Mode NOEKEON and Indirect Mode NOEKEON. Although cryptanalysis showed that Indirect Mode NOEKEON was vulnerable to related-key cryptanalysis the authors contend that the attacks are not a practical concern and due to its design their cipher is still useful. Related-key attacks are not possible on Direct Mode NOEKEON.

Joan Daemen and Vincent Rijmen also submitted a proposal to NIST during the AES selection process. Fifteen ciphers were shortlisted and Rijndael was the winner. Rijndael is a family of ciphers with different key and block sizes. Three ciphers were selected and are now known as AES (block size 128 bits, key lengths: 128, 192 and 256 bits). AES was subsequently adopted by the US government and superseded the Data Encryption Standard (DES).