A session management function of a 5G system receives information that a secondary authentication is to be done for a given user equipment for authorising user equipment to use a data network; and responsively to the received information, communicates with the data network and receives from the data network an indication; and allows a 5G access to the user equipment so that the user equipment can communicate with the data network according to the indication either without cryptographic protection or with cryptographic protection depending on the indication.