Central 4.0 and peripheral 4.2

[ponlakshmi]

Hi I am using Nrf51 and Softdevice S130.I know that softdevice S130 supporting Ble 4.2.This will act as a peripheral.My mobile phone supporting only Bluetooth version 4.0.When making connection to these tow devices what will be security level.In this case can we use the ECDH for application level encryption.

[bjorn-spockeli]

No, both sides of the link must support LE Secure Connections, (i.e. support BLE v4.2) in order to use the ECDH (Elliptic Curve Diffe-Hellmann) key exchange in the Link Layer.

If you want to implement ECDH encryption at the Application Layer, then you can use the Secure Bootloader's Cryptography library in SDK v12.x to generate public keys and compute the shared secret key.

Best regards

Bjørn

[ponlakshmi]

I am sure that the smart phone which is now available in the market not coming with BLE version 4.2.Is any other way to use ECDH key exchange protocol when the mobile device(Central) having BLE version 4.0. Using ECDH protocol is depend on Smart phone BLE Version or the APP which we are using to connect to the BLE 4.2 Device.

[bjorn-spockeli]

You will not be able to use the built-in ECDH encryption in the Link Layer unless both sides of the link support BLE v4.2.

If you want to implement ECDH encryption at the Application Layer, then you can use the Secure Bootloader's Cryptography library in SDK v12.x to generate public keys and compute the shared secret key.

I will edit my answer to reflect this.

[ponlakshmi]

yes i want to use the ECDH at application level.My mobile phone(redmi 3s prime) will act as a central which having bluetooth version 4.1.But my peripheral is Nordic nrf52 with softdevice S132.Is it still possible to use the ECDH at the application level for advertising data encryption.

[bjorn-spockeli]

Yes, that should be possible using the cryptography library from SDK v12.x.