dh-rl.py

from cryptography.hazmat.primitives.asymmetric import dh
from cryptography.hazmat.primitives import serialization, hashes
from cryptography.hazmat.primitives.kdf.hkdf import HKDF

# Generate our own private key and public key
parameters = dh.generate_parameters(generator=2, key_size=2048)
private_key = parameters.generate_private_key()
public_key = private_key.public_key()

# Serialize the public key and send it to the other party
serialized_public_key = public_key.public_bytes(
    encoding=serialization.Encoding.PEM,
    format=serialization.PublicFormat.SubjectPublicKeyInfo
)
# The other party receives the serialized public key and deserializes it
received_public_key = serialization.load_pem_public_key(
    serialized_public_key,
    backend=default_backend()
)

# Generate our shared secret
shared_secret = private_key.exchange(received_public_key)

# Generate a key from the shared secret using HKDF
derived_key = HKDF(
    algorithm=hashes.SHA256(),
    length=32,
    salt=None,
    info=b'',
    backend=default_backend()
).derive(shared_secret)