encryption of link and data

There are two terms we use in encryption

1) Enrypting a link between devices
2) encryption of data to be transmitted in between devices

I had seen these terms in bluetooth host and controller.

So are they one or same thing or both terms are having different meanings?

Enrypting a link between devices

Click to expand...

http://en.kioskea.net/contents/69-bluetooth-how-it-works
So basically for the link encryption the master finds devices available and sets them in a mode where they can create a piconet. It sends a certain parameter (I believe it's timing) during pairing that only the master and the slave knows. This can be sniffed during connection but only at the direct time that packet is sent out. Now the master and slave have a certain timing and hopping scheme that are in sync and only those two devices know. Therefore the link is encrypted.

The data encryption is where the data is packaged in a certain way to be sent to the other device. There is a frame architecture that can be looked up that has a structure that is directed only for only the target device to receive and read (there is an access code and header features).

So they are different as one is the method for which devices are secured for communication and the other is how the information is packaged and sent to the other device.