SHARK

SHARK
General
Designers	Vincent Rijmen, Joan Daemen, Bart Preneel, Antoon Bosselaers, Erik De Win
First published	1996
Successors	KHAZAD, Rijndael
Cipher detail
Key sizes	128 bits
Block sizes	64 bits
Structure	Substitution–permutation network
Rounds	6

In cryptography, SHARK is a block cipher identified as one of the predecessors of Rijndael (the Advanced Encryption Standard).

SHARK has a 64-bit block size and a 128-bit key size. It is a six-round SP-network which alternates a key mixing stage with linear and non-linear transformation layers. The linear transformation uses an MDS matrix representing a Reed–Solomon error correcting code in order to guarantee good diffusion. The nonlinear layer is composed of eight 8×8-bit S-boxes based on the function F(x) = x⁻¹ over GF(2⁸).

Five rounds of a modified version of SHARK can be broken using an interpolation attack (Jakobsen and Knudsen, 1997).

References

Vincent Rijmen, Joan Daemen, Bart Preneel, Anton Bosselaers, Erik De Win (February 1996). The Cipher SHARK (PDF/PostScript). 3rd International Workshop on Fast Software Encryption (FSE '96). Cambridge: Springer-Verlag. pp. 99–111. Retrieved 2007-03-06.{{cite conference}}: CS1 maint: multiple names: authors list (link)
T. Jakobsen, L.R. Knudsen (January 1997). The Interpolation Attack on Block Ciphers (PDF/PostScript). 4th International Workshop on Fast Software Encryption (FSE '97). Haifa: Springer-Verlag. pp. 28–40. Retrieved 2007-01-23.
Joan Daemen; Vincent Rijmen (2002). The Design of Rijndael: AES—The Advanced Encryption Standard. Springer-Verlag. ISBN 3-540-42580-2.