Note: This article lists the technical specifications of the YubiKey 4C. If you're looking for setup instructions for your YubiKey 4C, see https://www.yubico.com/start.
The YubiKey 4C has five distinct applications, which are all independent of each other and can be used simultaneously. Note: Some software such as GPG can lock the CCID USB interface, preventing another software from accessing applications that use that mode.
Interface
The YubiKey 4C uses a USB 2.0 interface. All of the applications are available through this interface.
Applications
OTP
The OTP applet contains two programmable slots, each can hold one of the following credentials:
- Yubico OTP
- HMAC-SHA1 Challenge-Response
- Static Password
- OATH-HOTP
USB Interface: OTP
U2F
The U2F application can hold an unlimited number of U2F credentials and is FIDO certified.
USB Interface: FIDO
OATH
The YubiKey 4 series can hold up to 32 OATH credentials and supports both OATH-TOTP (time based) and OATH-HOTP (counter based). Accessing this applet requires Yubico Authenticator.
USB Interface: CCID
PIV (Smart Card)
This application provides a PIV compatible smart card. On Windows, the smart card functionality can be enhanced with the YubiKey Smart Card Minidriver.
Supported Algorithms:
- RSA 1024
- RSA 2048
- ECC P256
- ECC P384
USB Interface: CCID
OpenPGP
This application implements version 2.0 of the OpenPGP Smart Card specification which can be used with GnuPG. For key sizes over 2048 bits, GnuPG version 2.0 or higher is required.
Supported Algorithms:
- RSA 1024
- RSA 2048
- RSA 3072
- RSA 4096
USB Interface: CCID
Physical Specifications
Form Factor
Connector: USB-C
Dimensions: 12.5mm x 29.5mm x 5mm
Weight: 2g
Temperatures
Operational range: 0 °C to 40 °C (32 °F to 104 °F)
Storage range: -20 °C to 85 °C (-4 °F to 185 °F)