How to change "id" in url

If my website is : web.com/index.php/z_tbl_user/update/119.
What i afraid is then visitor could change it to be this : web.com/index.php/z_tbl_user/update/120.
To prevent this i want to change so the visitor see is something like this  :   web.com/index.php/z_tbl_user/update/whscbscbxncbxn922.
So how to change the 119 to be some alphabet that is random?Are there any library or function? I google but i still confuse how to implement
Thanks for help.