Chip Card Interface Device (CCID) protocol is a USB protocol that allows a smartcard to be connected to a computer via a smart card reader using a standard USB interface, without the need for each manufacturer of smart cards to provide its own reader or protocol. This allows the smart card to be used as a security token for authentication and data encryption, such as that used in Bitlocker. Chip card interface devices come in a variety of forms. The smallest CCID form is a standard USB dongle and may contain a SIM card or Secure Digital card inside the USB dongle. Another popular device is a USB smart card reader keyboard, which in addition to being a standard PC USB keyboard, has an additional slot for accepting a smart card.