I'm starting to feel like I'm shilling Estonian eID (I'm not, just a regular citizen), but I think that system is the very least a cool proof of concept (if not

I'm starting to feel like I'm shilling Estonian eID (I'm not, just a regular citizen), but I think that system is the very least a cool proof of concept (if not a state of the art example) how public crypto can be used to sign and encrypt.