decadentist Ohh okay, but I thought passkeys are stored on the Titan M2 RISCV chip, are they not?
They can be stored on the local device's secure element, but as far as I know this is not a user-facing choice with Play services. In some cases Play services will give you the choice to store a passkey on the local device, but last time I tested that those passkeys got cleared when I reinstalled or deleted app data for Play services. So not something I would rely on, and doesn't seem to be an option for Whatsapp.
Storing passkeys to the secure element is unfortunately not a native feature to AOSP. A GrapheneOS developer has said in the past that they want to implement that feature for Vanadium. There is an open GitHub issue for it.
decadentist And to get saved there there needs to be a app which is responsible to managing the passkeys, correct? From my perspective this seems to be a non optimal implementation.
I agree. In Vanadium it's possible – but support being unreliable – to register passkeys also on an external security key – but yes, you need a third-party app to do so. You can do that with Play services or using an app such as HW Fido2 Provider. The latter also supports them being stored locally (to the secure element?), but there's no interface to manage them yet. I wrote a guide on how to (mostly) overcome the bugs with security key usage on Vanadium, but I'm not sure it's up to date anymore.
I don't know if even stock Pixel OS gives you the option in Whatsapp to save a passkey to a security key. That is possible on stock Pixel OS with Play services in general but Whatsapp can also disallow it.
W1zardK1ng Passkeys are implemented as a replacement for passwords, if passkeys are stored on devices how you can use it when you migrate to a new device or on your PC. Normally passkeys will be stored to the linked google or apple accounts, but you can use third party password managers like keepassdx or bitwarden to store them.
The FIDO Alliance decided to highlight cloud-syncable passkeys in their promotion campaigns on passkeys. I guess because that's a user-friendly approach for most people. That doesn't mean it's the only option.