I am trying to develop a scheme for generating unique (probable within bounds) ids in a distributed application. I want the id to be easily remembered, easily spoken, and easily read. I chose base32 as the encoding method, as it gives a large set of characters, universally recognised, and without confusion between similar looking characters.
So, if I have a set of 32 characters, and an id of length 4, I have $32^4$ (1048576) permutations, so the chance of a collision when a new id is created is something like one in
total-existing-ids - which is too much of a chance.
I think $32^6$ is reasonable as a trade off between memorability, and chance of collision, but it is harder to remember and read 6 random base32 characters.
I find it much easier, if all the numbers and letters are grouped, so where it might have been
e4hu8a I find
ehua48 much easier to remember/read/speak. Or
So, finally, my question...
How much entropy do I lose by my scheme of rearranging totally random base32 strings so letters come before numbers (but remain in the original order amongst themselves)?
How can I calculate the entropy for different length strings using this method?