03-11-25, 10:30 PM
Passkey in ASP.NET Core Identity: Modern Authentication for Secure Applications
Passwords are dead. That’s been a running joke in tech for years, but with recent changes to .NET, it’s finally starting to ring true. With .NET 10, the Microsoft team introduced native Passkey support in ASP.NET Core Identity—a huge leap forward for both security and user experience.
What are Passkeys?
Passkeys use the WebAuthn and FIDO2 standards to let users log in with biometrics or a device PIN, without ever storing a password or secret on the server. The private key always stays secured on the user’s device (like a phone, hardware token, or computer); only a useless-to-an-attacker public key is stored on your server.
When logging in, the server sends a random challenge, which the device signs with the private key; the server verifies the signature with the public key. Phishing: blocked. Brute-force: impossible. Database leaks: no more password hashes to worry about. From a user’s point of view, it’s just “scan your finger” or “look at the camera”—done.
Why Now?
Support for Passkey is growing. Modern browsers, password managers, and devices understand WebAuthn, making it a practical choice for real-world projects. Even mid-range laptops support biometrics now, and cross-device syncing is available in tools like 1Password and Bitwarden.
But there are caveats: if someone loses their only Passkey and can’t recover it, account access can be a nightmare. Good UX needs backup options.
Passkey vs. Passwords
Traditional systems rely on “something you know” (the password) plus “something you have” (your phone for SMS, etc). Passkey updates this: “something you have” (the device with the key) plus “who you are” (biometrics) or “what you know” (device PIN). This subtle shift drastically improves both usability and security.
How does ASP.NET Core Identity support Passkey?
.NET 10 introduces Passkey as a first-class citizen in Identity. The SignInManager now supports methods to create Passkey registration and authentication options, verify them, and handle user flows end-to-end.
Passkey integration in ASP.NET Core Identity marks a significant step toward passwordless, user-friendly, and robust authentication. With careful implementation, you can deliver a seamless login experience that’s much more secure than old-school passwords—no more “123456” or stolen credentials in leaks.
KingSkrupeLLoS
Passwords are dead. That’s been a running joke in tech for years, but with recent changes to .NET, it’s finally starting to ring true. With .NET 10, the Microsoft team introduced native Passkey support in ASP.NET Core Identity—a huge leap forward for both security and user experience.
What are Passkeys?
Passkeys use the WebAuthn and FIDO2 standards to let users log in with biometrics or a device PIN, without ever storing a password or secret on the server. The private key always stays secured on the user’s device (like a phone, hardware token, or computer); only a useless-to-an-attacker public key is stored on your server.
When logging in, the server sends a random challenge, which the device signs with the private key; the server verifies the signature with the public key. Phishing: blocked. Brute-force: impossible. Database leaks: no more password hashes to worry about. From a user’s point of view, it’s just “scan your finger” or “look at the camera”—done.
Why Now?
Support for Passkey is growing. Modern browsers, password managers, and devices understand WebAuthn, making it a practical choice for real-world projects. Even mid-range laptops support biometrics now, and cross-device syncing is available in tools like 1Password and Bitwarden.
But there are caveats: if someone loses their only Passkey and can’t recover it, account access can be a nightmare. Good UX needs backup options.
Passkey vs. Passwords
Traditional systems rely on “something you know” (the password) plus “something you have” (your phone for SMS, etc). Passkey updates this: “something you have” (the device with the key) plus “who you are” (biometrics) or “what you know” (device PIN). This subtle shift drastically improves both usability and security.
How does ASP.NET Core Identity support Passkey?
.NET 10 introduces Passkey as a first-class citizen in Identity. The SignInManager now supports methods to create Passkey registration and authentication options, verify them, and handle user flows end-to-end.
- Registration: The client calls an endpoint to get registration options. The user must already be logged in the usual way, for safety. Once the options arrive, the browser API (WebAuthn) generates a key pair. The public key and some metadata are sent to the server, which validates everything and saves it in a new
table.Code:AspNetUserPasskeys
- Authentication: Logging in works by requesting a challenge, signing it on the device, and returning that signature for verification. No passwords, no TOTP codes.
- Error handling is vital—users get friendly messages for common issues like timeouts or unsupported browsers.
- Keys and metadata are stored as JSON in the database. Multiple Passkeys are supported per user (for phones, tokens, laptops, etc.).
- Attestation is disabled by default for privacy, but can be added for strict enterprise needs.
- Browser-side JavaScript handles Passkey registration and login flows smoothly, with compatibility fallbacks for non-modern browsers.
- For migrations, a new database table is added, with foreign key links to the user. Old passkey implementations may need manual migration.
- Warn users about hardware limits (e.g., YubiKeys might only hold 25 Passkeys).
- Consider UX when users lose devices; have backup login options, not just Passkey.
- Use strong defaults for operation timeouts and make error messages clear for non-technical users.
- Monitor and log errors in attestation and signature verification with as much detail as possible.
- No out-of-the-box backup/export for Passkeys: users and admins need education.
- Attestation validation must be custom if strict hardware trust is needed.
- Cloud-synced Passkeys work browser-side, not server-side.
- Multiple registration attempts or race conditions can cause temporary user confusion.
Passkey integration in ASP.NET Core Identity marks a significant step toward passwordless, user-friendly, and robust authentication. With careful implementation, you can deliver a seamless login experience that’s much more secure than old-school passwords—no more “123456” or stolen credentials in leaks.
KingSkrupeLLoS