Rabbit was designed by Martin Boesgaard, Mette Vesterager, Thomas Pedersen, Jesper Christiansen and Ove Scavenius.
Cryptico had patents pending for the algorithm and for many years required a license fee for commercial use of the cipher which was waived for non-commercial uses.
The mixing function is entirely based on arithmetical operations that are available on a modern processor, i.e., no S-boxes or lookup tables are required to implement the cipher.
If, however, the attacker targets a large number of keys at once and does not really care which one he breaks, then the small IV size results in a reduced security level of 96 bit.
[6] A small bias in the output of Rabbit exists,[7] resulting in a distinguisher with 2247 complexity discovered by Jean-Philippe Aumasson in December 2006.