FIDO2 keys for Delta: which ones work and how to set them up

Compatible devices, recommendations, and common issues

Delta uses FIDO2 for multi-factor authentication. If you need a physical security key, choose a model that supports FIDO2/WebAuthn: Delta allows you to register multiple keys to the same account. For most users, a Yubico Security Key is enough, while a YubiKey 5 makes sense if you also need OATH, PIV, OpenPGP, or other additional protocols.

Below you will find FIDO2 keys for Delta, a quick comparison of the main models, and setup steps checked against the current official Delta instructions. If reliable access is important, it is better to register both a primary and a backup physical key and store them separately.

FIDO2 keys for Delta: compatible models

For Delta, the main requirement for a physical security key is FIDO2/WebAuthn support. In Yubico’s lineup, both the Security Key Series and YubiKey 5 Series work for this purpose. For Delta itself, the difference is not basic compatibility but the connector, form factor, and additional protocols.

• Security Key C NFC — a straightforward USB-C and NFC option if you mainly need FIDO2.
• Security Key NFC — the same idea for devices with USB-A.
• YubiKey 5C NFC / YubiKey 5 NFC — a better fit if you also need OATH/TOTP, PIV, OpenPGP, or other features beyond Delta.
• Models without NFC can also work with Delta through a compatible USB connector, but Delta’s official iPhone instructions use NFC when pairing a physical Yubico key directly on iOS.

Comparing Yubico models

Security Key vs YubiKey 5: what is the difference?

Both series support FIDO2/WebAuthn and work as physical security keys for Delta. Security Key Series focuses on FIDO2 and U2F, making it the simpler option if you mainly need a security key for account sign-in.

YubiKey 5 Series adds protocols that can be useful for work and more technical setups:

• PIV (Smart Card) — for enterprise authentication and certificate-based workflows.
• OpenPGP — for encryption, digital signatures, and signing Git commits.
• OATH-TOTP/HOTP — for one-time codes managed through Yubico Authenticator.
• Yubico OTP and Challenge-Response — for specific enterprise and technical use cases.

What does not work, and what should you check?

• Older FIDO U2F-only keys without FIDO2/WebAuthn support are not suitable for Delta: the current system documentation requires a FIDO2-capable device.
• Legacy security dongles without FIDO2/WebAuthn are also best avoided, even if they are marketed as two-factor authentication keys.
• A YubiKey running firmware earlier than 5.7 is not automatically incompatible with Delta as long as it supports FIDO2. However, Yubico documents a known Infineon ECDSA vulnerability affecting older YubiKey 5 Series and Security Key Series devices; exploiting it requires physical access and specialized equipment. If you are buying a new key, choosing a current hardware version is preferable. See the official Yubico security advisory for details.

Where to get a key for Delta and what to know

Where can you get a physical FIDO2 key for Delta?

The official Delta Wiki says physical USB FIDO2 keys can be ordered for system users through their unit. If you are buying a key yourself, check that it supports FIDO2/WebAuthn and has the connector or NFC support you need. We also have a separate comparison of current models: Best FIDO2 security keys to buy in 2026.

Can you copy a Delta security key?

No. A standard hardware FIDO2 key cannot be copied to another physical key like a file. Each registration creates its own cryptographic key pair, and the private part remains inside the authenticator. That is why a backup key must be registered separately in Delta while you still have access to your account.

Can the same key work on a computer and a phone?

Yes, as long as the key and the device have a compatible connection method. On a laptop, that usually means USB-A or USB-C; on a phone, NFC or USB-C is often the most convenient option. For pairing a physical Yubico key on iOS, however, Delta’s current instructions specifically use NFC. If pairing fails on Android, Delta recommends registering the key from a computer.

What FIDO2 is, in brief

FIDO2 uses public-key cryptography. When you register with Delta, the device or physical key creates a key pair bound to delta.mil.gov.ua: the private part remains in the key’s protected environment, while the public part is registered with the service.

Because the credential is bound to the legitimate domain, a phishing copy of the Delta login page cannot get a valid authentication response from your key. For a broader explanation of FIDO2, passkeys, PINs, and backup keys, see our separate guide: FIDO2 Security Key: How to Protect Google and Other Services.

Setting a PIN on a physical security key

Delta uses the FIDO2 PIN on a physical security key. How you create it depends on the platform and whether the key has already been configured.

On a computer: Windows, Linux, macOS

When you pair a new key, the browser will prompt you to create a PIN. If the key has already been used, enter the PIN that was set previously. With a YubiKey, you can also manage the FIDO2 PIN through Yubico Authenticator.

On Android

On Android, a new key may also prompt you to create a PIN during pairing. Delta notes that physical-key setup does not work on every Android device; its current guidance is aimed at modern Android versions and Chrome. If pairing does not work, Delta recommends registering the key from a computer. This limitation applies to setup, not to later sign-in from Android.

On iPhone/iPad: Yubico over NFC

To pair a physical Yubico key on iOS, Delta’s official instructions require you to set the PIN first in Yubico Authenticator. The key is then paired with Delta on iPhone over NFC.

1. Install Yubico Authenticator from the App Store.

2. Open the app, tap the three-dot menu in the upper-right corner, and open the configuration menu.

3. Open the PIN management section.

4. When the app asks you to scan the key, hold it against the iPhone’s NFC area until the scanning prompt disappears.

5. Set a PIN for the key and confirm it by tapping “Set”.

6. Hold the key against the NFC area again to write the PIN. Once the process completes successfully, you can close Yubico Authenticator.

Registering a security key in Delta

Delta publishes current step-by-step instructions for Windows, Linux, macOS, Android, and iOS in its official two-factor authentication Wiki. Use it as the primary reference because screens and individual steps can change.

If your account has just been activated, Delta sends an email with a link to set up two-factor authentication. If you already use the system, you can add another key from your profile in the list of registered FIDO2 keys.

• Do not unplug a physical key while the pairing process is still in progress.
• If the key is new and does not yet have a PIN, the system will prompt you to create one; on iOS, the PIN for a Yubico key must be set in advance.
• On iOS, Delta’s current instructions pair a physical Yubico key over NFC; this procedure does not work over USB-C.
• Give each key a clear name so you can easily distinguish the primary key from the backup later.

Signing in to Delta with a physical key

After registering the key, open the official Delta login page, enter your username and password, choose the security-key sign-in option, connect or tap the physical key, enter its PIN, and confirm by touching the key. System prompts differ across Windows, Linux, macOS, Android, and iOS, so use the official Delta guide for the current step-by-step screens.

You can also use a physical key on a smartphone if the phone supports the required interface. Separately, Delta allows a phone or tablet itself to act as a FIDO2 key when signing in on another device; in that scenario, both devices need an internet connection and Bluetooth must be enabled.

Common issues, support, and a lost key

The key is not recognized

• Try another USB port and, if possible, connect the key directly without a hub. If you use an adapter, make sure it supports data transfer.
• Check the browser. Delta notes that Chrome has the broadest support; Firefox, Edge, and Safari are also supported, but behavior can vary depending on the device and configuration.
• On Android, if you cannot pair the physical key, complete registration from a computer. Delta’s official Wiki specifically notes that signing in from Android can still work afterward.
• On iPhone, pair a physical Yubico key over NFC as described in Delta’s current instructions.

The browser does not show the security-key prompt

• Make sure you opened the official delta.mil.gov.ua domain and selected the physical security-key option on the screen.
• Try another supported browser. Delta recommends Chrome for most scenarios, although the available sign-in options can differ by operating system.
• If the key is currently open in Yubico Authenticator or another application, close that application and try again.

The PIN is not accepted

• Make sure you are entering the PIN for the key itself, not your Delta, phone, or computer password.
• YubiKey allows eight FIDO2 PIN attempts. After the limit is reached, FIDO must be reset and all FIDO registrations on that key need to be created again. We cover this scenario in more detail in our FIDO2 security key guide.
• Do not reset the key blindly: a reset deletes its FIDO data, so first make sure you have another way to recover access to the accounts you need.

The key works on a computer but not on a phone

• For a USB connection, check whether the phone supports data transfer through that port or adapter.
• For NFC, make sure NFC is enabled and hold the key against the phone’s antenna area for a few seconds.
• If the problem happens during pairing rather than sign-in, keep the platform limitations in mind: on iOS, Delta currently documents pairing a physical Yubico key over NFC; on Android, if setup fails, it recommends moving to a computer.

If the key is lost or damaged

If you still have another registered key or device and can sign in to Delta, remove the lost key from the list of registered FIDO2 keys in your profile.

If the physical key or device has fallen into someone else’s hands, Delta’s official Wiki says to contact the Delta Cybersecurity Department immediately: Element @delta_security:delta.mil.gov.ua, Signal / WhatsApp +380 63 297 67 68.

If you need help restoring access, contact Delta technical support: Element @delta_support:delta.mil.gov.ua, WhatsApp +380 98 297 67 68. Once access is restored, register a new backup key. If you need a replacement, see our current FIDO2 key recommendations.

Conclusion

If you need a physical FIDO2 key for Delta without extra features, start with Security Key NFC or Security Key C NFC depending on the ports on your devices. YubiKey 5 Series makes more sense if you also plan to use the same key for PIV, OpenPGP, OATH/TOTP, or other workflows.

For a reliable backup, it is better to have two separately registered physical keys and keep them in different places. For registration, sign-in, and account recovery, always check the current Delta Wiki, because system screens and platform support can change.

If you are still choosing a model, start with our 2026 FIDO2 key comparison. If you already have a key and want to set it up for other services, see our separate practical FIDO2 guide.