It was the easiest one to get at, that was already on the host's PHP installations, openssl. The purpose of them is generating nonces using a hash function on, probably, a time string, or so, which would ensure that there was no duplicates in thousands of iterations, but nothing specifically identifying. I used the ripemd160 hash because I know it's pretty resistant to collisions. I mean, I could implement the necessary function with a simple increment but it's more code, basically.
The algorithm just automatically generates a string, one for 'user' and another for individual items for each user, so they can bookmark the link with the query string containing the 'user' code, and from that there is a database with user code (or nothing), item code, and a datestamp.
I did it this way because I figured it was the shortest, quickest way to generate unique IDs for each user. Something like a weaker version of the elliptic curve that is used for Steem. With steem, the username is not actually important, in fact I don't know where it actually appears, I am thinking probably in the initial.
But it doesn't matter so much, so long as there is no duplicates, and I know of no better way to ensure this within what will probably be at most maybe 20,000 'users' and amongst their items, the combination should yield a unique key for each entry.
It is just, really, a quick and dirty database application purpose, I will reveal exactly what it is for once it is up and running. I have got the answer to the question about the server configuration that I need, and the capabilities for the application, so I am just waiting on my 'boss' to make the subscription, and move the domain over to the new host that allows what I require.
Once it's complete and I've polished it with some nice CSS, next I will look into how to build a google chrome extension that integrates with it. Then the user can just set their UUID with it, and hopefully, I can then get it to automatically populate a form item that will mean they can use this with all of their posts automatically.
I imagine that if you are a clever person you probably have some idea what the purpose is, but I think I will get the jump on this and have something people can start using right away with little inconvenience.