[dependenttypes]

Would you happen to know what kind of signature scheme they use?

[mschuster91]

IIRC the German system is proprietary, the specs are available only after payment of a couple hundred euros.

[dependenttypes]

I am grossed out by proprietary protocols but proprietary encryption algorithms just make me laugh. Who even though that this would be a good idea? Are they seriously trusting their money with this?

[icebraining]

I don't know about the German system, but here they use EMV-CAP: https://en.wikipedia.org/wiki/Chip_Authentication_Program

[dependenttypes]

No public key crypto?

[Fnoord]

My bank seems to use a similar scheme. It appears akin to TOTP with 8 numbers. But the secret is inside the black box. They also have something like a QR code but with RGB colors (does not work with blue light reducing features).