Which U2F Key is the most secure?

EmLeX932 Don't get me wrong, this is a great device, but the topic is about comparing security - not every use case requires strongest possible security. I think this is especially great middle ground for someone not willing to manage multiple keys, or could actually remember a strong password (use only for this one case, not in multiple places).

I get that you can store strings securely in OnlyKey, it could be useful feature for many things, but a Smartcard does all of this without possibility of reading the private key - all computation happens on device over standardize protocols. BTW. Yubikeys without Smartcard functionality are 2x cheaper.

DeletedUser43 I think this is especially great middle ground for someone not willing to manage multiple keys, or could actually remember a strong password (use only for this one case, not in multiple places).

Yea. Apologies for going a bit overboard with info. just felt like was important to get out too as part of discussion. Onlykeys can be set up in such a way that NO DATA can be pulled back out of them

I started taking notes on a side, here's my comparison table:

| Feature\Device.....| Yubikey..| Nitrokey..| OnlyKey..|
| Unique-unforgeable..| yes......| yes...... | no...... |
| Updatable.......... | no...... | yes...... | yes......|
| Smartcard.......... | yes......| yes...... | no...... |
| Passkeys............| 128......| 50?...... | 12?......|
| NFC................ | yes......| yes...... | no...... |
| IP68................| yes......| no........| yes......|
| Backup..............| no...... | no........| yes......|
| Long-term cost......| $$$......| $$........| $........|

EmLeX932 I'm getting into a territory which is over my head, but one last comment: Yubikey's and Nitrokey's main power is a hidden, unreadable, permanently fused (unchangeable) key, which is a base for all cryptography done by them. With them, you get a design which tries to give physical guarantee, they are unique and unfordable. I'm guessing here, but OnlyKey by allowing for an option to do back up, can't provide this property.

DeletedUser43 The firmware update feature is a potential attack vector as well. This is why Yubikey doesn't allow it.

I recall not having been able to find an official statement by Yubico on the topic of secure firmware upgrades. Would be interested in seeing a source for that last sentence.

fid02 Not in the same words, but:

To prevent attacks on the YubiKey which might compromise its security, the YubiKey does not permit its firmware to be accessed or altered.
https://support.yubico.com/hc/en-us/articles/360013708760-YubiKey-Firmware-is-Not-Upgradable

It's a brick wall instead of a secure door kind of situation.

SerenityNow Well, I'll give you my opinion, I had a high threat model at a certain level and I changed jobs last years. Now I use an iPhone because my wife decided to have an iPad and you know when you set foot in it it's over... in short I still had my fido keys and my basic security procedures, and then a few months ago we had our personal data stolen from Free including iban. I went to my banker to see what we could do and he clearly told me that without my signature no one can withdraw money from my account even with an iban! So no... following this appointment I decided to let go of a lot of leste and abandon my fido keys, and to keep only the simplest: double authentication with phone number or passkey when it is available. I rely on the security of my phone which is the best thing to do with Google pixels.

Guillaume And it has nothing to do with the discussion but I would like to take the opportunity to point out that ProtonPass is on sale with a unique and LIFEtime offer!

DeletedUser34

Back in May 2024 a GrapheneOS developer mentioned the Trezor Safe 3 as what they consider a more secure alternative to FIDO2 with Yubikeys (source).

Quote:

https://trezor.io/trezor-safe-3 has a decent secure element and can be used for FIDO2, and using it requires unlocking it with a PIN with secure element enforcing a max attempt limit

that's not the main purpose of that but it can be used for FIDO2, SSH, PGP and other things like that despite it not being the main use

fid02 Outside of it main purpose, the documentation is terrible. Someone please send sources if I'm wrong somewhere.
It's an interesting device for u2f if you already use it for crypto, but it's more lie OnlyKey than Yubikey or Nitrokey.

It's not unique and unforgeable. It has a secure element, but the main key is not derived from unreadable hidden key, but from a dice password you remember. So in practice everything I talked about OnlyKey applies.
No NFC, not waterproof. There is some documentation on GPG, but it looks like it doesn't work as standard Smartcard. Isn't it only a backup for GPG stored inhome directory?

Updated table:

| Feature\Device......| Yubikey..| Nitrokey..| OnlyKey..| Trezor..|
| Unique/unforgeable..| yes......| yes...... | no...... | no......|
| Updatable.......... | no...... | yes...... | yes......| yes.... |
| Smartcard.......... | yes......| yes...... | no...... | no......|
| Passkeys............| 128......| 50?...... | 12?......| no?.... |
| NFC................ | yes......| yes...... | no...... | no......|
| IP68................| yes......| no........| yes......| no......|
| Backup..............| no...... | no........| yes......| yes.... |
| Long-term cost......| $$$......| $$........| $........| $...... |