a small number of rounds. However it was broken in 1996 by Thomas Jakobsen and Lars Knudsen, using interpolation attack. Denote by SHARK(n,m,r) a version of SHARK with block size nm bits using n parallel m-bit S-boxes in r rounds. Jakobsen and Knudsen found that there exist an interpolation attack on SHARK(8,8,4) (64-bit block cipher) using about 2^{21} chosen plaintexts, and an interpolation attack on SHARK(8,16,7) (128-bit block cipher) using about 2^{61} chosen plaintexts.
