In fact, googling around seems to indicate (via non-authoratative sources which have partially been deleted) that it sets the U2F counter based on the current unix timestamp when the U2F applet is installed/reinstalled, which would imply that you cannot have a backup ledger, unless you delete and reinstall the applet each time you want to use the opposite device. If I had to guess, I'd say that there's probably a real-time clock in the device, or that it gets the current time when it interacts with the Ledger Live app, and then the usage counter is updated in that manner to correctly spoof logins. I have no idea how Ledger gets around this.

It always has to be greater (by 1 or more than one) than the last successful login. If you cloned a Yubikey and then used the master 10 times, when you went to use the backup it would fail because the usage counter would now be behind the last value seen by the website. With YubiKey 4, you now must: Trust Yubico to have uploaded firmware known to them to have no vulnerabilities in the OpenPGP implementation. ago It's an issue of trust and one you can not escape. One is that there is a counter, typically per device but theoretically it could be per account, that increments each time an action is preformed. Does anyone know any good alternative to Yubikey 3 13 13 comments Best Add a Comment frumious 7 yr. I cant see anything related to it on previous screenshot. The original FIDO U2F has inherent mechanisms to prevent cloning. Updated: Marian H - How can Yubikey be used as storage for a keyfile When I enter PIN of Yubikey I get this screen What should I select Some says that PIV certificate can be used as a keyfile.

Yubikey open source alternative