Security Concepts
The acronym CIA stands for confidentiality, integrity, and availability.
Note
Messages may be data, code and the whole computation device as a whole.
Confidential: we only want the people that we want to to be able to read our messages. May apply to things that are at rest like storage, or things that are in motion like network traffic. We are concerned with the ability authenticate and have the user be someone we can trust, the ability to authorize and grant them only the necessary privileges, and to create privacy so that outside actors can't eavesdrop on communication.
Integrity: we want to insure that our messages haven't been tampered with. We use things like cryptographic checksums to help ensure that the contents of files are what we expect them to be. We want messages to be correct and know that they are from a certain source. We want to know our messages were received and we want to have some confidence on the flow of transactions.
Availability: the message is available when needed. Includes protection against denial of service attacks. We want to ensure our service uninterupted and we want to design fairness so that the access to the system is equally distributed.