How short can a GUID be?

Question

I know the standard GUIDs. Can they be made shorter? What is the theory behind it?

Answer 1

They are exactly 16 bytes.

Technically speaking the effect of shortening them will vary based on the algorithm used to generate them. Considering, the API you used (probably) doesn't guarantee a particular version or implementation, it's a bad idea to shorten them. Even if it did, it's a bad idea. If you require less than 16 bytes of entropy, you should prob not be using a GUID.

For more information: http://en.wikipedia.org/wiki/Globally_Unique_Identifier