After upgrading to macOS Catalina, the YubiKey option is greyed-out. This means its price needs to be higher to be able to cover the development costs. The YubiKey feature is used by a small number of people.

Why is the YubiKey in-app purchase so expensive? After running some tests, having read the documentation and evaluated the amount of time and work that would need to be put toward implementing this feature, the truth is that the user base for such a feature just isn't there and as a small developer, we'd rather invest this time and effort into improvements and upgrades that will have a broader and more immediate impact. Unfortunately, at this time we don't intend to provide support for YubiKey in iOS. Why aren't the iPhone and iPad supported? Yes. pwSafe's usage of the YubiKey is exactly the same as Password Safe's. Is pwSafe compatible with safes from Password Safe? To ease the creation of backups keys, the secret is also stored in encrypted form inside the safe itself.

The password you enter is used as the challenge and the resulting response is used as the safe password. When the key is initialized, a random secret is stored in it.

PwSafe uses YubiKey's HMAC-SHA1 challenge response mode. An YubiKey is a security token which serves as a second authentication factor.

Yubi key ios