By now you have probably heard about the "death of passwords," or at least alternatives to them. Passkeys are one such alternative. Apple, Google, and Microsoft are rolling them out. https://tinyurl.com/PasskeySupporters They are intended for use in remote login to web based applications. (While apps can use passkey, many are already passwordless.) PayPal, Kayak, Best Buy, eBay, GoDaddy, and Google are among those that are offering Passkeys as a preferred alternative means of user authentication.
Passkeys resist the security problems with passwords. They eliminate both the choice of password requirement and the forgotten password problem. They resist brute force and replay attacks. Social engineering (e.g., so called "phishing") attacks no longer work. While the user may still be duped into logging on, the process that that uses does not leak reusable information.
(However, Passkeys may still leave one vulnerable to session stealing (MitM) attacks. This is a limitation that they shares with most remote authentication methods. Note that unlike the reuse of passwords, MitM attacks do not include the ability to initiate sessions, only takeover sessions initiated by the legitimate user. They also require the ability, usually by duping the user, to insert a process between the user and his target application.)
Passkeys are an application of asymmetric key cryptography. The private key is stored on a user side device and is used to sign a challenge (random value sent from the application side.) Every time one chooses to sign on to an app or a web application with a passkey, one must authenticate to the device by biometric or PIN.
Thus Passkeys offer strong authentication. One must possess the device holding the private key, something that one has, and the biometric, something that one is, or PIN required to open the device and again at time of use. The exchange of the challenge and response resists replay.
Most often, and at least in the short run, apps that implement Passkeys will leave their use at the option of the user. It will be offered as an option, either at enrollment time or when signing on. If one accesses an account from multiple devices, one may create a passkey for the account on multiple devices. Apple plans to store keys in the cloud, as does now with passwords, so that one key can be used across multiple Apple devices sharing access to one Apple account.
When attempting to logon to an account that expects a passkey from a device that does not already have access to a key, one may be offered a QR code to sync to a device that does have access to a (or the) key. Both the security and the convenience are maintained.
Indeed security and convenience are what Passkeys are about. They make it easier to do the right thing than the wrong thing. Smart enterprise applications will offer them as an option and smart users will choose them. Some enterprises will mandate them. They offer us one more opportunity to increase the cost of attack against our networks, systems, applications, and data while improving convenience.
What are your questions?