The invention relates to a method for authorized updating of first operating software of a field device which is used in an automation technology installation, wherein an authentication test of second operating software for the field device is performed, which second operating software is signed by means of a first private key associated with the installation, wherein, within the scope of the authentication test, the signature, generated by the first private key, of the second operating software is authenticated by means of a first public key associated with the installation, and wherein, in the event that the authentication test has been performed successfully, the first operating software located on the field device is at least partially replaced by the second operating software.