many, however, effectively all of the smartcard hardware implementations are proprietary. The most open one I can think of is the OpenPGP card which is PC/SC st

many, however, effectively all of the smartcard hardware implementations are proprietary. The most open one I can think of is the OpenPGP card which is PC/SC standard compatible. It's sold by Free Software Foundation Europe and is colloquially known as the "foundation" card. However, while the applet source that runs on the Java card is available, I don't know about the firmware or runtime libreness. It's be really great to have an auditable open source processor/soc design with PC/SC compatible interface and secure enclave implemented in an ISO standard smartcard form factor. Alas, to my knowledge nothing like that exists. Yubikey designs used to be a lot more open than they are currently (you used to be able to run your own applets, IIRC - with some security compromises, of course). That said, I would still personally use them for non-critical things - it's a really handy form factor.