Cryptographic algorithms are typically used to meet one or more security goals:

• Authentication: Simply put, authentication is how we prove that a user is who they claim to be. Through the process of authentication, we ensure that a user's identity is verified. The process of authentication starts by having the user present their identity. This is followed by providing information that is only known by the user and so can only be produced by them.
• Confidentiality: Data that needs to be protected is called sensitive data. Confidentiality is the concept of restricting sensitive data to authorized users only. To protect the confidentiality of sensitive data during its transit or in storage, you need to render the data so that it is unreadable except by authorized users. This is accomplished by using encryption algorithms, which we will discuss later on in this chapter.
• Integrity: Integrity is the process of establishing that data has not been altered in any way during its transit or storage. For example, TCP/IP (Transmission Control Protocol/Internet Protocol) uses checksum or Cyclic Redundancy Check (CRC) algorithms to verify data integrity.
• Non-repudiation: Non-repudiation is the concept of a sender of information receiving confirmation that the data was received and the recipient receiving confirmation of the sender's identity. This provides irrefutable evidence that a message was sent or received, which can be used later to prove the receipt of data and the points of failures in communication.