What does nrf51822 AES Encryption actually encrypt?

[George]

I am working on a BLE device (currently being prototyped with the mbed DK). It connects to a smart phone app. I would like to build in some security features, definitely some form of Transport Layer Security. Are there any other aspects I should be protecting?

Mbed TLS and the Nordic encryption features both seem to work on encrypting data to be sent. Is that correct?

If so, which should I use?

[Vidar Berg]

You can enable encryption of the link using the security manager mentioned here. This allows a central to bond with your device in order to establish a secure connection.