Confidentiality is concerned with keeping information secret. It is a key information security objective.

A cipher can be used to achieve confidentiality. As an example, if Alice wishes to communicate secretly with Bob, then they would choose a keypair (e,d) which would give the encryption function Ee and the decryption function Dd. If Alice's plaintext is m then Alice sends the ciphertext c=Ee(m) to Bob. Bob can then compute the original plaintext as Dd(c)=m.


A. Menzes, P. van Oorschot, and S. Vanstone, Handbook of Applied Cryptography. CRC Press, 1996.