Earlier quoted context omitted.
> Passkeys absolutely do not need TPM. They do not, but how does the service you’re using know your passkey is secure? For all they know you’re just some gullible user that clicks through every fishing email you get. You’re dumb, weak, helpless, they gotta protect you from this scary world out there, and maybe yourself as well. They can’t do that if they allow your passkey to be stored anywhere you control. KeepassXC…
> For all they know you’re just some gullible user that clicks through every fishing email you get. Passkeys are non-phishable. That's part of their schtick. I'm not a huge passkey fan myself, but this is a real benefit.
When the passkey is protected behind an HSM (TPM, Yubikey, Tkey…), even a compromise of your main computer can’t steal it. Attackers can still temporarily log in on your behalf, but they can’t do anything with your passkey as long as your computer is turned off. Which means you can un-pwn yourself out of this situation by reinstalling everything (but do keep your HSM!).
Overall, we have several levels of security here:
- Weak password, (potentially reused everywhere). Fished once, pwned everywhere. Not to mention password database leaks.
- Very strong unique password from your password vault (KeepassXC). Note that with automatic login, password managers may provide good phishing resistance. Manual copy pasta is still vulnerable, but at least you only compromise that one account.
- Passkey stored in your password database. Phishing proof as you say, but falls to a keylogger.
- Passkey sorted in a hardware security module. Can’t be stolen ever, save for a vulnerability in the HSM itself, or, if you haven’t set up a password for your HSM, theft.
Clearly that last option is the most secure. Clearly it would be nice if everyone could do that, though we do need a way to recover from the loss or destruction of the HSM (which in the case of the TPM may mean something as mundane as changing your graphics card). Yet often, other ways are more convenient.
Still, I strongly believe companies should not force people into one method or another. Okay, I could maybe tolerate passkeys being forced on me, but not the remote attestation part. Let me manage my own security, with my own tools (preferably open source), thank you very much. There is one use case for which I may approve of remote attestation: work accounts. Because at this point it’s not about the safety of the customer, it’s about the safety of the company itself. It makes sense then that the company (or government agency) impose whatever stringent restrictions on how to access their network. They do have to provide any required tool (company laptop, company palmtop, company dongle…), same way many companies are required to provide individual safety equipment to any of their employees working in hazardous environments.