unity AR ios game

Hi, I have unity ar game for ios. this game is a complete with everything but I want one fuitures, In the game we are writing the user name at the first screen, then we kill the zombies from random. when the game is over writes score. Just I want unique id for username and highscore table. way is not important (firebase, with xml ,mysql...) -very small work - !! -MY BUDGET İS ONLY $10- !! Project this game is a very simple game and have 3 scene start, main and gam over. in start scene we can wright username for examle 'myname' and with start button enter the game , in game we can kill zombie for example we have 10 kill, if the zombies kill us, the game over scene is coming we can see 'myname' = 10 .. just I want the user name to be unique and save the score on game over scene ( highscore ) does not matter where it is save score ( database, xml... )