Yubikey 5Ci

CTAP 2.1

Supports CTAP 2.1, including features like enforced PIN complexity, credBlob, largeBlob, and alwaysUv

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FIDO2 Certification

Certified by the FIDO Alliance as conforming to FIDO2 standards

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FIDO L2 Certification

Certified by the FIDO Alliance to meet L2 Security Standards

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HOTP passwords

Supports Hashed One-Time-Password generation

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Management Application

Vendor provides applications that extend or configure the device

Android management application

Management application runs on Android smartphones with appropriate hardware (NFC, BLE, etc)

iOS management application

Management application runs on Apple iOS devices

MacOS management application

Management application runs on MacOS

Windows management application

Management application runs on Windows

Resident Cryptographic Keys

Supports WebAuthn discoverable resident credentials, the building block of passkeys

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Resident ECDSA keys

Supports ECDSA discoverable keys

Resident ED25519 keys

Supports ED25519 discoverable keys

PKCS#11 SmartCard

Conforms to PKCS11 SmartCard interface standards

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Stored passwords

Supports stored, static passwords, usually configured with a vendor-specific application

Timed OTP passwords

Supports Time-based One-Time-Password generation

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U2F Authentication

Conforms to the U2F Authenticator and WebAuthn standard

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YubiOTP

Enables use of Yubico YubiOTP one-time-passwords

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The Yubikey 5Ci is the only mass produced security key that pairs a USB-C connector with an Apple Lightning connector. For users on iPhone 14 or older, or older iPads with Lightning, this is the most direct way to use a hardware key on iOS without going through NFC.

Apple’s move to USB-C on the iPhone 15 and later means the Lightning side of this key is increasingly legacy. Yubico still sells it, and a FIPS variant is also produced, but no successor model has been announced. New iPhone owners will probably be better served by the Yubikey 5C NFC, which uses NFC for tap to authenticate against current iPhones.

The 5Ci supports the full Yubikey 5 protocol stack: FIDO2, U2F, OATH HOTP and TOTP through the Yubico Authenticator app, PIV smart card, OpenPGP, YubiOTP, and static passwords.

EUCLEAK

Like the rest of the Yubikey 5 family, the 5Ci is in scope of the EUCLEAK side channel disclosed in September 2024. Firmware 5.7 contains the fix and units shipping after May 2024 are not affected. See the Yubikey 5 entry for the full background.