It was a little joke I'm afraid, because you can't reverse the hash, so you need to store it somewhere. Most of the existing link shorteners are a variant on th

It was a little joke I'm afraid, because you can't reverse the hash, so you need to store it somewhere. Most of the existing link shorteners are a variant on this idea. There are RFCs I think about content addressable storage if you're interested in that sort of thing, this is sort of like content addressable addresses if you see what I mean :), and someone else mentioned a distributed hash table, which is an interesting idea.