I don't see what the problem is. For example, you could do this: create a string->"final string" hash function, where heißt and heibt both hash to the same final string (let's say it's HEIBT). You're only allowed to register final strings. If I create a company called heißt.com, then going to heibt.com (or HeIbT.com, hêìbŤ.com, or whatever) will also go to that same domain. A company can use heißt.com if it likes, or hêìbŤ.com, or whatever it prefers. But a spammer can't create a lookalike string. Why wouldn't this work?