What is the probability of guessing (matching) a Guid?

Question

Just curious but what is the probability of matching a Guid?

Say a Guid from SQL server: 5AC7E650-CFC3-4534-803C-E7E5BBE29B3D

is it a factorial?: (36*32)! =

Answer 1

There are a number of things wrong with your calculations. First off, 36*32 implies that any alphanumeric character can be part of the GUID. This is not the case; only HEX characters are allowed.

Secondly, the calculation for the number of unique GUIDs is Number of Valid Characters (16: 0-9, A-F) ^ length of GUID (32 characters )

So we have 16^32 ==> 2^(4^32) ==> 2^128

The odds of guessing any one GUID is 1 / 2^128.