Yubikey 5Ci
: Resources & Documentation
The Yubikey 5Ci
The YubiKey 5Ci is the first dual-connector hardware security key designed to provide absolute protection across heterogeneous ecosystems. Featuring a USB-C interface on one end and a Lightning connector (for iPhone, iPad, and Mac) on the other, it eliminates the need for adapters to secure your access. It’s the multi-protocol solution of choice for Apple device users (external link) who work across computers or tablets equipped with modern USB-C ports.
Technical Specifications for the Yubikey 5Ci
Interfaces & Connectivity
The YubiKey 5Ci features a dual physical connector: a USB-C interface (USB 2.0-compatible) and an Apple MFi-certified Lightning interface. All built-in security features are fully available and functional on both of these separate ports.
OTP (One-Time Password) Module
The OTP applet includes two programmable, independent slots. Each slot can be configured independently to store and generate one of the following types of identifiers:
Yubico OTP
HMAC-SHA1 Challenge-Response
Static Password
OATH-HOTP (Counter-based)
OATH Module (Application-Based Two-Factor Authentication)
The YubiKey 5Ci can store up to 32 OATH credentials (supporting both time-based OATH-TOTP and counter-based OATH-HOTP protocols). These codes are accessed and managed through the Yubico Authenticator app.
OpenPGP Module
This submodule implements the OpenPGP specifications for smart cards and integrates natively with GnuPG for encryption, digital signing, and SSH key authentication.
Protocol Updates: Version 2.0 of the OpenPGP specifications is enabled by default. Starting with firmware version 5.2.3 (and later), the key implements version 3.4 of these specifications.
Software requirement: To use key sizes greater than 2048 bits, GnuPG version 2.0 (or later) is required on the host operating system.
Supported basic algorithms: RSA 1024, RSA 2048, RSA 3072, RSA 4096.
Additional Algorithms (Firmware 5.2.3 and later):
Elliptic curves: secp256r1, secp256k1, secp384r1, secp521r1
Brainpool: brainpoolP256r1, brainpoolP384r1, brainpoolP512r1
Edwards/Montgomery: curve25519, x25519 (decryption only), ed25519 (signature and authentication only)
Physical specifications
Form factor: Rigid dongle with dual symmetrical connectors.
Connectors: USB-C and Lightning (MFi-certified).
Dimensions: 18 mm x 45 mm x 3.3 mm.
Weight: 2.9 g.
Environmental resistance: Rugged design with no battery or moving parts, effectively protecting the internal chips from everyday wear and tear.
Safe operating temperature ranges:
Operating temperature range: 0 °C to 40 °C
Storage temperature range: -20 °C to 85 °C
FIDO2 / WebAuthn Protocol
Supports secure single-factor, multi-factor (2FA), or completelypasswordless authentication.
Storage capacity: This module can store up to 100 resident keys (Passkeys / discoverable identifiers).
Enhanced security: Your login credentials are protected locally by a PIN that you set yourself.
Authentication Mechanism: Once the key is unlocked with your PIN, simply touching one of the two side touch sensors confirms your physical presence and instantly logs you into your accounts. The FIDO2 app is certified by the FIDO Alliance.
FIDO U2F Protocol
The U2F (Universal 2nd Factor) app is certified by the FIDO Alliance. It allows users to generate and store an unlimited number of credentials to serve as a second factor of authentication (2FA) that is impervious to phishing.
PIV Module (Smart Card)
This module provides a smart card interface that complies with PIV (Personal Identity Verification) standards. In the Microsoft Windows environment, the device's integration and performance are optimized through the use of the official YubiKey Smart Card minidriver.
Default values and secrets:
PIN:
123456PUK code:
12345678Management Key:
010203040506070801020304050607080102030405060708
Supported algorithms: RSA 1024, RSA 2048, ECC P256, ECC P384.
Slot Architecture and Mapping:
Slot 9a: AuthenticationSlot 9b: Management KeySlot 9c: Digital SignatureSlot 9d: Key ManagementSlot 9e: Card AuthenticationSlot f9: CertificateSlots 82-95: Retired Key Management
Documents related to the Yubikey 5Ci
Video(s) related to the Yubikey 5Ci
How to - Yubikey and Google (English)
Introduction - Yubikey and Facebook (English)
Introduction - Yubikey and DropBox (English)
Introduction - Yubikey and Windows Hello (English)
Introduction - Yubikey and MacOs (English)
Introduction - Yubikey and Tweeter (English)
Introduction - Yubikey and GitHub (English)
