Use AES256-GCM to decrypt some ciphertext with a provided key and nonce.

DeriveSharedKey uses HKDF to derive a key from a shared secret and public keys.

Use AES256-GCM to encrypt some plaintext with a provided key.

generatePublicPrivateKey uses curve25519 to generate a public and private key pair.

GenerateSharedSecret uses the private key and the other party's public key to generate the shared secret.