The US driver's license barcode has a signature nobody can check — and the keys were never included

This is a great investigation but I have two small nits:

> the ZNB field is not empty and not garbage: it contains a well-formed 71-byte DER ECDSA signature, correctly Ascii85-encoded, with the right prefix and a plausible length. But it fails the cryptographic check instantly, because it was signed with somebody else's key.

Seems doubtful! I expect the forgers used a real signature from another card instead, so it has the right key but the wrong data. Reverse engineering the process as the author did and making up their own key wouldn't be of any value to the forgers.

> I built a little demo to check the signatures across California, New York, and Virginia: take a picture of the barcode and check it here.

This is not wrong, but should come with a little warning. A real verifier needs to additionally check the encoded data matches the human-readable data on the front of the card.

I didn't realize that "over the counter" delivery of drivers licenses was not the normal method. When I get a new driver's license at the DMV, I go to a self serve kiosk, have my picture taken, then walk over to a room and my license is already printed by the time I get there. They have 3 massive card printers (imagine a laser printer, but 6 ft/182.88 cm long). It event prints a pseudo-hologram.

I have to surrender my old license to the person in the room. How does that work if your license is mailed to you? Do you get to keep the old one?

I think mDL is going to be a pretty big deal in some industries (e.g. banking). Apple announced an ecosystem around this at WWDC25. Very soon we are going to be in a world where you walk into a bank to open/maintain an account and the following occurs:

1. The bank emails/SMSes the customer a link

2. The customer takes out their iPhone, opens whatever email/messaging software & taps the link

3. The link takes the customer to a specially crafted page owned by the bank that triggers a native OS process for opening Apple Wallet and gathering requested ID details with consent.

https://developer.apple.com/videos/play/wwdc2025/232

https://www.w3.org/TR/digital-credentials

This is potentially a superior arrangement because it could eventually establish a strong cryptographic chain of trust all the way to the issuer (e.g. the State of Alabama). Right now there are some gaps in that chain but I see no reason they couldn't be closed over time.

All of this is nearly pointless unless the photo itself is in the barcode and also signed. You only need a leak of a few hundred real IDs to cover all of the identifiable characteristics (hair, eye, skin color, approx height and weight). Leak a few hundred thousand a year and now you can’t even flag leaked IDs without some false positives.

A fake photo plus a valid barcode will pass any current check right? Unless you still do a secondary proprietary photo lookup that I don’t think exists.

Should credit the authors of the Verifiable Credential library. The vendor isnt the one to credit here.

Digital verification is going to matter a lot more for objects we own rather than the objects that proxy for that (currently the main function of an ID). Identity fraud is only problematic because ownership is tied to a loose record of SIN/DL.

Having a physical medium represent ownership just shifts the burden to the state and allows for social engineering and fraud to persist.

I had a fake ID, and it being scannable was a huge selling point. Convenience stores all scan, and don't seem to care if you look underage. I was only turned down two or three times, usually at bars and restaurants.

Colloquially, we could say: States now issue drivers licenses cards having both a readable number and an authentication code; the state could provide a way for the public to check if the drivers license is true by verifying the authentication code, but they don't provide this service.

..

When discussing asymmetric cryptography with less technical folk, a lock analogy breaks down quickly as locks are conceptualized as being symmetric. Hence, "key" is a poor word that came from symmetric cryptography; one really needs to discuss the signature or authentication code.

A better analogy may be a transparent display case, where only authorized people can put things into the case. To check a copy outside the case is true, one would want to go to the official display case and compare. This isn't a great analogy because there's no analog to the signature, but it gets the asymmetry across.

Perhaps we might do a bit better? Suppose your friend gave you a poster copy of a famous painting from the Metropolitan Museum. On the poster is the curatorial accession number. You could go to the MET and check if your poster matches the painting, which should have matching accession number on the label.

So far our analogy covers asymmetry but is still centralized. The museum also distributes a catalog of its posters/paintings. Catalog entries have a thumb print of the painting and its accession number. So, if you could find a trusted copy of that catalog, say at your local library, you might also us […]