Scene; iWannaKnow HQ, the Boss's Office. Those present: Dave, the Pointy-Headed Boss. Frank, a representative Customer. Hal, the Technical One.
Dave: "We want to generate a unique identifier for every customer. If only there were some alphanumeric string we could use that would be totally unique so we would know we were tracking the same customer's voice to ensure consistency."
Hal: "We could use the device serial number but that would break privacy laws."
Dave: "Oh. Hey, I know, we could cut the serial number in half, reverse each half, and stick them back together! Let's do that!"
Dave: "We also need it to only last 6 months, then we need to allocate a new unique identifier to that customer. Hey, I know, we could deallocate the number I just thought of and add it back to the pool of random unique identifiers, and allocate the customer with the latest unique identifier number that has been freed up!"
Frank: "That sounds like a great idea! Can we teach Siri to lip-read as well?"
Hal: "I still have the greatest confidence in your honesty and integrity, Dave..."