def read_chain_pair(private_key, certificates):
    """
    Read private key and certificates from files.
    Return (private key, certificates) chain pair.
    """
    with open(private_key, 'rb') as f:
        private_key = f.read()
    with open(certificates, 'rb') as f:
        certificates = f.read()
    return (private_key, certificates)