Smart cards store certificates and private keys. You can use a smart card reader to import certificates from a smart card to the key store on your BlackBerry smartphone, but you can't import private keys. As a result, private key operations such as signing and decryption use the smart card, and public key operations such as verification and encryption use the public certificates on your smartphone.
If you use a smart card certificate to authenticate with your smartphone, after you connect your smart card reader to your smartphone, your smartphone requests authentication from the smart card each time that you unlock your smartphone.
You can install multiple smart card drivers on your smartphone, including drivers for microSD smart cards, but you can only authenticate to one smart card at a time. If you are authenticating using a microSD smart card and you want to transfer media files between your microSD smart card and your computer, you must temporarily turn off two-factor authentication or select a different authentication option.
If the S/MIME Support Package for BlackBerry smartphones is installed on your smartphone, you can use smart card certificates to send S/MIME-protected messages.