Not responding directly to your question, but it sounds like you want to hash something rather than generate a random value. I’d suggest looking into Plug.Crypto and JWTs.

Simple generation of seeded, URL-safe strings (github.com)

Here is my attempt at modifying the gist for seeded generation. I took the liberty of simplifying the code a bit into a Livebook.

I don’t have any experience with :rand so I don’t know if you need to reset the seed generation to pseudo-random after generating in randomize/3, to prevent it affecting other parts of an application.

In my opinion it seems a bit overkill to create a whole library for this, but that’s not relevant to the question.