Diffie-Hellman key exchange for Raspberry Pi and Arduino

The project is to create a very simple central key management scheme to be used with two micro-controllers, the Arduino Uno and the Raspberry Pi. The private/public key manager should have a database that stores public keys. The key scheme is basically a Diffie-Hellman key exchange to be implemented by the two micro-controllers mentioned above. The main goal of the project is to have the Arduino Uno and the Raspberry Pi connected to one laptop. This laptop will have a public key database for the Arduino's public key and the Raspberry Pi's public key. The Arduino will encrypt a message using its own private key and the Raspberry Pi's public key. This ciphertext (encrypted message) will be sent through Bluetooth to Raspberry Pi, and vice versa. The Raspberry Pi will decrypt the message using the Arduino's public key.