Bluetooth LE secure connection with wolfssl and nordic: key exchange

Question

I want to establish a secure Bluetooth connection from the client side with a nordic chip (nRF52). I also have the wolfSSL library running. So I receive a 'BLE_GAP_EVT_LESC_DHKEY_REQUEST' request from the nordic softdevice with the peer-64byte key. Now I need to generate my own key pair and send the public key back to the central. How can I manage this? Am I right that the following functions is not the correct one for the BTLE secure connection?

    wc_InitDhKey(...);
    wc_DhGenerateKeyPair(...);
    ...
    sd_ble_gap_lesc_dhkey_reply(...);

I need to generate a elliptic curve Diffie-Hellman key-pair with a P-256 length. Unfortunately I am not an expert in this topic. Which functions do I need to call from the wolfSSL library to generate such a public ECDH-key?

Thanks for your answer or hints

Answer 1

I suggest you too look at the documentation of the module curve25519 to generate an elliptic key:

https://www.wolfssl.com/wolfSSL/Docs-wolfssl-manual-18-10-wolfcrypt-api-curve25519.html

Answer 2

The confusion is that ECDH and DH got little in common but the name. I suggest looking at wc_ecc_shared_secret() and wc_ecc_make_key().