def METHOD_NAME(self, esn):
    """Create a key handshake request"""
    header = json.dumps({
        'entityauthdata': {
            'scheme': 'NONE',
            'authdata': {'identity': esn}},
        'headerdata':
            base64.standard_b64encode(
                self._headerdata(auth_data={}, is_handshake=True).encode('utf-8')).decode('utf-8'),
        'signature': ''
    }, sort_keys=True)
    payload = json.dumps(self._encrypted_chunk(envelope_payload=False))
    return header + payload