Symmetric encryption message authentication

Symmetric ciphers are commonly used to achieve other cryptographic primitives than just encryption.[citation needed]

Encrypting a message does not guarantee that this message is not changed while encrypted. Hence often a message authentication code is added to a ciphertext to ensure that changes to the ciphertext will be noted by the receiver. Message authentication codes can be constructed from symmetric ciphers (e.g. CBC-MAC).[citation needed]

However, symmetric ciphers cannot be used for non-repudiation purposes except by involving additional parties.¹

[1] https://en.wikipedia.org/wiki/Symmetric-key_algorithm#Cryptographic_primitives_based_on_symmetric_ciphers

See also

Protocol