The Yubikey Token is an USB device that emits an event based One Time Password. You can initialize the Yubikey using the YubiKey personalization tools. The secret hex key and the final OTP length are needed here. For tokens compatible with the Yubico cloud service the OTP length must be 44 (12 characters UID and 32 characters OTP). When programming the token for the Yubico cloud service, the Public Identity Length must be 6 bytes, which will give you a UID with 12 characters. The current OTP length of a programmed YubiKey can automatically be determined by inserting it in the test field.