Comment by Linux-Fan
The signature function of the German ID card (“neuer Personalausweis”).
Its 2025 and we still haven't solved secure online identification and we are still not using end-to-end encryption for e-mail, most e-mail is not even signed.
Interaction with state agencies is still mostly via paper-based mail. The only successfully deployed online offer of the german state administration seems to be the online portal for tax filings “elster.de”.
The use of a private key on the national ID card would have been able to provide all this and more using standard protocols.
At least for identification, there is an expensive effort to re-design something similar in a smartphone-centric way and with less security and not based on standard approaches called “EUDI wallets”.
For encrypted communication the agreed-on standard seems to be “log in to our portal with HTTPS and use our proprietary interfaces to send and receive messages”...
Why did it die: Too expensive (~30€/year for certificate, >100€ for reader one time) and too complicated to use. Not enough positve PR. Acceptance at state-provided sites was added too late. In modern times, everything must be done with the smartphone, handling of physical cards is considered backwards hence this is probably not going to come back...
Edit: Anothther simiarly advanced technoloy that also seems to have been replaced by inferiror substitute smartphone: HBCI banking (a standard...) using your actual bank card + reader device to authenticate transactions... replaced by proprietary app on proprietary smartphone OS...
Some countries turned it into a part of their national ID system. Has worked great for the past 15 years. You can get a card reader for less than 20€. Works under any OS really. I can't remember the last time I got physical mail that wasn't some item I ordered.
S/MIME died because it is in many ways worse than CDOC and ASiC-E containers over email. People are reviving such approaches with EIDAS2 and from that ERDS (Electronic Registered Delivery Service). But there are no EU-wide implementations as of yet.
Those app-based approaches have also appeared, because well, they don't require a card reader. Though I'd rather see something NFC-based with a physical card. I personally find phone vendors' HSMs (and their equivalents) haven't seen enough scrutiny. Plus the apps are proprietary.
The demand is definitely there, but I predict it'll take at least a decade for the rest of the EU to catching up to Estonia, Finland and a few others. Just 25 years later.