As an added layer of security, PayPal also offers a PayPal Security Key, which is a portable device that creates a six-digit code every 30 seconds. The user links this key to his or her eBay or PayPal account. The six-digit code is used in conjunction with the user ID and password to create a unique security code. This extra service requires either a one-time purchase of $29.95 for the device or a mobile phone with text messaging to receive codes from a virtual key (the mobile service's SMS charges apply)