Estonia gives everyone a smart card they can use to digitally sign things. Obviously someone can steal your card but it's pretty hard to forge otherwise.
It's a solved problem, just nobody wants to fix it.
How much trouble are you in if your card gets stolen?
Would you call a number to temporarily block it, and a fine to get a new one? If so, how does the call authenticate you?
Second question, "pretty hard to forge otherwise", is about roughly how hard? Has it been proven possible / proof of concept? Or did you mean to say you're unaware of any successful forgeries but (naturally/obviously) can't honestly claim it's totally impossible, because you never know.
I'm real curious about the Estonian smart card thing. Does it work well? Can you only sign government things with it, or really just about anything that needs your authentication? (say, commercial contracts) Does it have a private/public key type of thing so that you could also encrypt something with someone's public key so that only that one individual cardholder can ever decrypt it?
It's a solved problem, just nobody wants to fix it.