Passkey

A Passkey is a modern, secure method of user authentication that replaces traditional passwords with cryptographic key pairs. Designed to be phishing-resistant and user-friendly, passkeys allow users to sign into websites and applications using biometric verification (like Face ID or fingerprint), a device PIN, or a security key—without ever having to type or remember a password.

Passkeys are part of the FIDO2 and WebAuthn standards and are backed by major tech companies including Apple, Google, and Microsoft. They offer a safer and more convenient alternative to passwords by eliminating common vulnerabilities such as weak passwords, reuse across sites, and exposure to phishing or credential theft.

Passkeys are stored on a user’s device and are encrypted, making them inaccessible to unauthorized applications or attackers.

How Do Passkeys Work?

A passkey uses a public-private key pair generated during account registration. Here's how it works:

1. Registration:

   • The user registers with a service (website/app) using a biometric or PIN-based verification.

   • A public-private key pair is created. The public key is sent to the service, while the private key stays securely on the user's device.

2. Authentication:

   • When logging in, the service sends a challenge.

   • The user unlocks their device with biometrics or PIN.

   • The device signs the challenge with the private key.

   • The service verifies the response using the stored public key.

This process confirms the user's identity without transmitting sensitive secrets across the internet.

Structure of Passkey Authentication Systems

A typical passkey system includes:

• Credential Manager: Manages and stores the passkeys locally or in a secure cloud vault (e.g., iCloud Keychain, Google Password Manager).

• Authenticator: The device or component (e.g., biometric sensor, security key) used to unlock and sign authentication requests.

• Relying Party: The website or application that receives and verifies the passkey-based login.

• FIDO2/WebAuthn APIs: Standards that enable passkey creation, registration, and authentication in supported browsers and apps.

Benefits of Passkeys

• Phishing-Resistant: Cannot be tricked by fake websites because no password is typed or shared.

• Device-Based Security: Private keys never leave the device, reducing risk of theft.

• User Convenience: No need to remember or enter complex passwords.

• Cross-Platform Syncing: Many systems support syncing passkeys across devices through secure cloud services.

Examples of Where Passkeys Are Used

• Apple Devices: Face ID or Touch ID with iCloud-synced passkeys.

• Google Accounts: Passkey logins using Android devices or security keys.

• Passwordless Login for Apps: Increasingly adopted in finance, healthcare, and enterprise platforms.