“A yet to be invented DNA reader would be a perfect credit card pin number.”
Too slow and too intrusive.
Use electronic thumb prints. The DMV’s have a device that copies, measures and records your thumb print in about a minute.
I had the “pleasure” of renewing my Ca. Driver’s license yesterday, and I had my thumb print electronically recorded 3 times in one hour.
Retinal scanning will be even faster and more reliable than the electronic thumb print gear.
Just go with both. For a “welfare” system. Cut down on the fraud. Just need to record the biological ID of millions. Fingerprints and retina scans.
My LG smart phone has fingerprint security id as do many other high end phones.