CODEWITHSUNDEEP
bluetoothbluetooth-lowenergybluetooth-lowenergy-4.2
SteffenH
SteffenH

Reputation: 107

Pairing differences between Bluetooth and Bluetooth LE?

Is there any (big) technial difference between pairing 'normal' Bluetooth devices and pairing Bluetooth LE devices?

I found a lot of information for Bluetooth LE pairing, but not for normal? For example Info 1.

So is this information for normal Bluetooth correct too?

Upvotes: 2

Views: 3220

Answers (1)

Preeti
Preeti

Reputation: 336

If you mean Bluetooth Classic or BR/EDR by 'normal',the difference depends on the version of Bluetooth in use.

Bluetooth Classic or BR/EDR 2.1 - 4.1 Vs BLE 4.0-4.1

  1. BR/EDR pairing procedures are handled by the LMP layer of the Bluetooth Controller.

    BLE Pairing procedures are handled by SMP in the host stack.

  2. BR/EDR uses ECDH Key generation which prevents passive eavesdropping.

    BLE legacy pairing does not use ECDH Key generation and so it is susceptible to passive eavesdropping

  3. BR/EDR defines 4 association models; OOB, Passkey entry, Just works, Numeric Comparison

    BLE Legacy Pairing defines 3 association models ; OOB, Passkey entry, Just works.

    Although they appear similar from the user perspective, they do not provide the same level of security. See #2

  4. BR/EDR generates the Link Key on both devices.

    BLE legacy pairing, generates the STK. The Link Key i.e. LTK in use is distributed by the slave

BR/EDR v4.2 Secure Connection vs BLE v4.2 Secure Connection

BLE 4.2 secure connections added ECDH key generation and the Numeric Comparison association model. It also did away with the STK. The LTK is now generated on both slave and master.

Secure connection association models on the BLE link, are equivalent to BR/EDR secure connection association models, in terms of protection against MITM attacks and Passive eavesdropping. When two BR/EDR/LE devices support Secure Connections over both transports, keys for both transports may be generated during a single pairing procedure. The ability to convert keys from one transport to the other eliminates the need to pair twice.

There are still some differences.

  1. BR/EDR pairing procedures are handled by the LMP layer of the Bluetooth Controller.

    BLE Pairing procedures are handled by SMP in the host stack.

  2. BR/EDR cryptographic functions use HMAC-SHA-256.

    BLE cyrptographic functions use AES-CMAC.

More information can be found in the Bluetooth core specification here

Upvotes: 6

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