Are Face ID and Passkeys the Same? Exploring Key Differences.

Two concepts frequently discussed in this space when looking to improve user authentication systems are Face ID and passkeys. While both involve modern forms of authentication, they are fundamentally different in design and application.

In this article, we'll dive into these key topics:

1. Is Face ID the same as passkeys?
2. Passkeys vs. biometrics: What’s the difference?
3. How do passkeys work?

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Is Face ID the Same as Passkeys?

The short answer is no. Face ID and passkeys are not the same, though they can complement each other in a seamless authentication experience. Here’s a breakdown:

• Face ID is a biometric authentication system that uses the unique features of your face to unlock your device or access specific apps and services. It’s a form of biometric identification, which means it uses a physical trait—your face—to verify your identity.
• Passkeys, on the other hand, are an authentication method that use a cryptographic key pair (a public key and a private key). Instead of entering a password, users authenticate using biometrics (like Face ID) or a device PIN to unlock a private key stored on their device, browser, or password manager. Passkeys are part of a broader move toward passwordless authentication, which enhances both security and convenience.

So while Face ID can be used as part of the authentication process when using passkeys, Face ID itself is not a passkey. Face ID is a method of biometric authentication, whereas passkeys represent an entire passwordless authentication system that could utilize biometrics like Face ID for user verification.

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Passkeys vs Biometrics: What’s the Difference?

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Passkeys: They provide strong authentication through the use of cryptographic key pairs—a public key and a private key—which are stored securely on the user’s device, browser, or password manager.

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In contrast to Face ID user verification, passkeys offer an end-to-end authentication solution. When a user wants to access your app or service, the private key is unlocked on their device, often using biometrics like Face ID or a PIN, and the authentication process is completed without the need to enter a password. 

This approach makes passkeys a highly secure and convenient method for verifying user identity, as their cryptographic process ensures resistance to phishing attacks by preventing the transfer of sensitive information over the internet.

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How do passkeys work?

Passkeys are built on public key-based authentication. During the registration process, your authenticator generates a public key, which is shared with the application, and a corresponding private key, stored securely on the authenticator. When the application issues a challenge, it encrypts the request using the public key. If the user successfully decrypts the challenge with their private key, they are authenticated into the application.

Below is a sequence diagram that shows the flow of data during both the registration and authentication processes of a passkey.

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Face ID is a biometric verification method primarily used as a screen lock, scanning the user’s facial features when reopening an app or web app to add an extra layer of security. Its main purpose is to confirm that the person accessing the app is the device owner. However, Face ID by itself is not a full end-to-end authentication system and does not offer strong authentication. The key difference is the cryptographic ceremony that involves a server-side validation.

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While Face ID provides a fast and user-friendly way to verify identity, it is typically part of a larger authentication process. For example, it can be used to unlock the private key needed for a passkey or to access secure apps. Face ID works in tandem with other systems, such as passkeys, to ensure a higher level of security.

Face ID is a valuable tool for identity verification, when used in a mobile native application it functions primarily as a screen lock mechanism. To ensure full security, it must be integrated into a broader authentication protocol, such as a FIDO2 passkeys.

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Passkeys offer a secure passwordless system, while biometrics act as a user-friendly way to unlock and access that system. They work together, but they are not the same thing.

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Looking to implement biometrics or passkeys into your app or service? Learn how Authsignal integrates with any identity stack for the best developer experience and faster deployment of biometric authentication and passkeys.

Authsignal also enables you to gain fine-grained control over your user authentication flows with our no-code rule engine. Start integrating for free today.