A Yahoo! Security Key is a personal access code (like the PIN you use at the ATM) designed to protect your most sensitive information displayed on Yahoo!.
Certain secure areas of Yahoo! require you to create a security key, in addition to your Yahoo! password, to gain access. After initial creation of your security key, you're prompted to verify your security key each time you attempt to access a secure area (such as Wallet, Account Access, or BillPay).
Once you create your security key, you should never give it to a non- Yahoo! site or another person, just as you keep your ATM PIN a secret.
Verification of your security key, as well as the display of your protected sensitive information, is always done over a secure (SSL) connection. For more detailed information on how this works, please read: