Yubico provides free personalization tools for the Windows, Mac and Linux platforms that allows you to re-initialize the AES key in your YubiKey.
The tools can also be used to configure your YubiKey to generate an OATH-HOTP 6 or 8 digit number, or to set a long static password which can be used even offline since it requires no validation server.
If you choose to re-initialize the AES key of your YubiKey, Yubico will not be aware of the new AES key and can't validate the One-Time Passcode (OTP) generated from it.
To validate OTPs generated from your newly programmed YubiKey, you need to host your own YubiKey validation server and put the same AES key in the server's database.
NOTE: To download YubiKey Personalization Tool via the App Store an Apple account is required.
· 64-bit processor