def save_private_key_to_pem(key: RSA,
output_stream: BinaryIO,
password: str,
protection: str = 'PBKDF2WithHMAC-SHA1AndAES256-CBC') -> None:
"""Save private RSA key
:param key: RSA key
:param output_stream: Output stream
:param password: Password
:param protection: Protection algorithm
"""
encrypted_key = key.export_key(passphrase=password, pkcs=8, protection=protection)
output_stream.write(encrypted_key)
