Pomaranch - Design and Analysis of a Family of Stream Ciphers ∗

Pomaranch is a synchronous, hardware-oriented stream cipher submitted to eSTREAM, the ECRYPT Stream Cipher Project. The cipher is designed as a cascade clock-controlled key-stream generator built on jump registers. This paper presents a discussion over the attacks on Pomaranch discovered so far. Particular focus is made on a new inherent property of jump registers that allows to construct their linear equivalences. For the concrete configuration of the registers in Pomaranch this allows to build an efficient key-recovery attack. Finally, a few tweaks that secure the cipher against the known attacks are sug-