Blowfish Weak keys

Question

I've read about the weak key issue with Blowfish, but can't seem to find anything that explains the practical effect of weak keys on Blowfish with the full 16 rounds.

Is there any actual attack upon non-reduced-round Blowfish, in the event that a weak key is chosen?

Answer 1

Yes there is an (unrealistic) attack on weak keys in Blowfish. Basically I just extend Vaudenay's original collision into the s-box to more collisions. The key space of Blowfish is so large that some keys will have many collision. Finding such a key is near impossible however.

There is also the more recent reflection keys attack on Blowfish that are quite interesting.