This is how you can add a security key to an Apple ID in iOS 16.3

Beginning with iOS 16.3, users can add a physical security key to their Apple ID as part of Apple's Advance Data Protection capabilities. Advanced Data Protection, which was unveiled in December, offers three methods for safeguarding user data. First off, additional iCloud services—including iCloud Drive, Apple Notes, Apple Photos, and others—now offer end-to-end encryption. Second, users have the option to use iMessage Contact Key Verification to confirm that they are only messaging the people they wish to. In the exceedingly unlikely case that an attacker compromises Apple's servers and intercepts iMessage chats, users who have it enabled automatically receive notifications for those talks. Third, iOS 16.3 will increase the level of security for an Apple user's Apple ID's two-factor authentication. It will enable access to an Apple ID sign-on using hardware security codes from external hardware security codes. When using two-factor authentication, a hardware security key is used to confirm that the person logging into an online account is the rightful owner of that account. They seem as tiny USB gadgets that can be plugged into a computer or wirelessly connected to a device via NFC or Bluetooth. The most well-known manufacturer of hardware keys is arguably Yubico. They have a number of variants that feature USB-C ports, NFC connectivity, and even an iPhone Lightning key. The most well-known manufacturer of hardware keys is arguably Yubico. They have a number of variants that feature USB-C ports, NFC connectivity, and even an iPhone Lightning key. In 2021, AppleInsider gave a Yubico YubiKey a positive review, awarding it a high 4.5 rating for its battery-free construction and wide range of online account compatibility.