DEAL (cipher)

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DEAL, the Data Encryption Algorithm with Larger blocks is a block cipher that was a candidate in the AES competition; it did not make it into the finals. Like all AES candidates, it uses 128-bit blocks and supports key sizes of 128, 192 or 256 bits.

DEAL is a Feistel cipher using DES as the F function. Six rounds were used with a 128-bit or 192-bit key and 8 rounds with a 256-bit key. The idea was originally proposed [1] by Lars Knudsen, but the AES submission was from Richard Outerbridge. Knudsen was a member of the Serpent team for AES.

DEAL has approximately the overheads of Triple DES, making it too slow to be a competitive candidate for AES. There were also some cryptanalytic results [2] [3] against the cipher.


  1. Lars Knudsen, DEAL - A 128-bit Block Cipher
  2. John Kelsey & Bruce Schneier (August 1999), Key-Schedule Cryptanalysis of DEAL, Springer-Verlag, at 118-134
  3. Stefan Lucks (1999), On Security of the 128-Bit Block Cipher DEAL [ booktitle = Fast Software Encryption (FSE '99), at 60-70