Encryption / Description Alphanumeric 16 digits

[eluser]stef25[/eluser]
You say "you can’t limit the result of the encryption to a fixed length string". Isn't that contradictory to "A hash always has a fixed length".

I agree with the method you propose. It's still an interesting question though. What I'd do is what you say, to use the first X characters of the hash with collision detection. The chance that this ads more than one or two queries to your app is pretty low.