Design of a centralized key management scheme using Arduino Uno R3 and Rasperry P -- 2 - open to bidding

The project is to create a very simple central key management schemes to be used with two micro-controllers, the Arduino Uno and Raspberry Pi. This 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 the 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 Arduini's public key. What i need: Code for a private/public key scheme (Diffie-Hellman key exchange) that can generate public/private key pairs and store keys in its database. I don't care which encryption algorithm you see, as long as it works. Arduino code to encrypt and decrypt a message using this scheme AND for bluetooth communication. Python code for Raspberry pi (or whatever language supported you like best) that does the same as for the Arduino. It is able to encrypt and decrypt message using that key scheme and bluetooth communication.