In cryptography, Zodiac is a block cipher designed in 2000 by Chang-Hyi Lee for the Korean firm SoftForum.
Zodiac uses a 16-round Feistel network structure with key whitening. The round function uses only XORs and S-box lookups. There are two 8×8-bit S-boxes: one based on the discrete exponentiation 45x as in SAFER, the other using the multiplicative inverse in the finite field GF(28), as introduced by SHARK.
Zodiac is theoretically vulnerable to impossible differential cryptanalysis, which can recover a 128-bit key in 2119 encryptions.
Further reading 
- HONG D, SUNG J, MORIAI S, LEE S, and LIM J (2002). "Cryptography and Information Security. Impossible Differential Cryptanalysis of Zodiac.". IEICE Trans Fundam Electron Commun Comput Sci. E85-A (1): 38–43.
- Wen Ji and Lei Hu (2008). "Square Attack on Reduced-Round Zodiac Cipher". Information Security Practice and Experience. Springer. pp. 377–391. doi:10.1007/978-3-540-79104-1_27. ISBN 978-3-540-79103-4.