According to its essential definition, network security should have the following basic characteristics: (1) confidentiality. Refers to the characteristics that information will not be leaked to or used by unauthorized individuals, entities and processes. All levels of the network system have different confidentiality and corresponding preventive measures. At the physical layer, it is necessary to ensure that system entities do not leak information by electromagnetic means. At the operational level, it is necessary to ensure that the system provides services according to the authorization, so that the system will not be used by unauthorized people at any time, such as hacker attacks, password attacks, illegal promotion of user rights, illegal use of resources, etc. (2) Integrity. Refers to the characteristics that information cannot be modified, destroyed, inserted, delayed, out of order and lost without authorization; (3) availability. Refers to the characteristics that legal users can access and use information in the required order, that is, to ensure that legal users can access information and related materials when needed.
In the physical layer, it is necessary to ensure that the information system can work normally in a harsh working environment. At the operational level, it is necessary to ensure that the system can always provide services for the licensor, ensure the availability of the system, and make the publisher unable to deny the published information content. The receiver can't deny the content of the received information, and uses digital signature to deny the data.