node/crypto Diffie-Hellman

This is a very basic example of how the Diffie-Hellman key exchange works when using node's crypto module.

Workflow:

• We first create a diffieHellman instance for Alice and generate keys for her.
• Then we create a diffieHellman instance for Bob using Alice's generator and prime number.
• Then both Alice and Bob computes their secrets individuall using each other's public keys.
• We simply assert that the secrets produced by both parties to be equal at the end.