The solution here seems to be some credentialing solution that can neither be given away voluntarily nor taken by force. Is such a thing possible?

I disagree, I don't think there is any need for proof of identity to not be voluntarily relinquishable.

I think relinquishable credentials are quite useful for a number of delegation related uses - but if they are relinquishable then they need to be expirable as well.

The guy with a knife won't ask for proof of identity that he knows you can't give up.

If a guy with a knife wants my password I'm going to give it up and walk away alive, then try and recoup the loss of whatever I gave up... maybe I get the debit against an account reversed or purge recent account activity from social media.

There currently is nothing secret like that that I'd give up my life to protect, and I can't conceive of anything of such import existing... for those cases where the item is truly dangerous (like the nuclear football) then a guy with a knife being a threat is already a failure of security.

the guy with the knife is why fingerprints retinal or iris scans, and facial metrics shouldnt be used.

You may not be able to give these things but they can be taken, using that knife.

You don't even have to be alive for those things either.

This is how iPhone works today. Apple bricks your phone if it is stolen, as a disincentive against theft.

Detached fingers don’t work with modern implementations of fingerprint sensors.

Oh, I was unaware of that - so I'm not certain I want to rely on the knowledge of someone in a position to cut off my finger... additionally, they don't currently work, but I'm sure there could be developed ways to spoof them by artificially circulating warmed blood or some such.

Just... biometrics are such a terrible idea - let's not even open that door.

the problem isnt weather or not its true, the problem is how likely someone is to try using a severed part any way, because it just might be FUD and a dead finger is just as good as attached. aside from that, a severed finger continues to live for a while afterward, it doesnt instantly perish. it has to metabolize its oxygen reserves.

The most popular and high priced phone has had fingerprint authentication since 2013. If there was going to be a rash of people cutting off fingers, wouldn’t it have happened by now?

If it happened would any PR department admit it? so far the tactic of waiting for someone to unlock a phone then robbing them has been effective. as soon as it becomes required behaviour it will happen. so far there are methods of hijacking a phone from its original owner, even without the phone in hand [simjacking] and as such tactics are stymied, other more brutal force methods would be required.

You really don’t think that would make the news? Why would you have to depend on the PR department? It sounds like another panic without any basis in reality.

And now, that phones are moving toward face recognition isn’t kind of a moot point?

I'm not convinced that's true.

A quick Google search....

https://www.iphoneincanada.ca/iphone-5s/will-your-severed-fi...

That spokespersons claim is plainly a lie though, refutable both in theory -- the given explanation is gobbledygook -- and in practice -- Chaos Computer Club has YouTube videos showing that fingerprint cloning works.

And that “proof” is of a first generation Touch ID, and unless you can find a reliable citation showing where a dead finger would work, how do you know it’s “gobbledygook”?

From a practical standpoint, if someone was willing to cut off your finger, wouldn’t it be easier to just force you a gunpoint to unlock your phone? Someone who really wanted what’s on your phone bad enough to try the “unreliable” hack, would just force you to unlock your phone or give up the password.