The WordPress wp_users table uses an ID that is an auto-increment integer for unique user ID.
There is no way to change that without making significant changes to the way WordPress works, and even if you do that, you will break most plugins that depend on the integer value for user ID.
I don't see any benefit from using hashed value for the ID. IDs are unique in a single installation of WordPress. ID in the form of number is the best solution for MySQL queries, database tables indexing, and other things. All websites today use numerical IDs for users for those reasons.