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CC2640R2F: Security with pre-defined Long Term Key

Addarsh Chandrasekar
Prodigy 250 points

Part Number: CC2640R2F

Hi,

I am using the example projects ble5_multi_role projects running on two CC2640R2F Launchpads, one as the client and the other as the server.

My SDK version is 1.35.00.33.

Is there an API for me to save the LTK (Long Term Key) and skip the pairing process? Since both devices only need to talk to each other, if they have the same pre-defined key stored in them, connection should always be secure  right? Let me know if this possible/ makes sense.

Cheers,

Addarsh

  • 0
    TI__Guru** 105180 points
    Hello,

    The Bluetooth specification does not allow for pre-sharing the LTK so there is no API for doing so. You can use OOB pairing, but that does require an exchange with the peer device. Note that more information is exchanged during the Pairing process beyond just the LTK.

    One option would be for you to encrypt the payload at the application layer with your shared key and not enable LE Encryption / Security.

    Best wishes
  • 0 in reply to JXS
    Prodigy 250 points
    Hi JXS,

    Thanks for your reply.
    If I set the pre-shared key as OOB data in both devices will that work?
    Also, in such a scenario. will a malicious attacker be able to sniff the keys during the pairing process?

    Cheers,
    Addarsh