def _extract_skid(self, file: pathlib.Path):
        out = subprocess.check_output(
            ['openssl', 'x509', '-in', file, '-noout', '-text'])
        lines = out.splitlines()
        for i, v in enumerate(lines):
            if v.decode("utf-8").find("Subject Key Identifier") > -1:
                skid = lines[i + 1].decode("utf-8").split()[-1].replace(
                    ":", " ").upper()
                break
        return skid