Editing Symmetric-key algorithm (section)

== Use as a cryptographic primitive ==
Symmetric ciphers are commonly used to achieve other [[cryptographic primitive]]s than just encryption.{{citation needed|date=April 2012}}

Encrypting a message does not guarantee that it will remain unchanged 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 an [[AEAD]] cipher (e.g. [[AES-GCM]]).

However, symmetric ciphers cannot be used for [[non-repudiation]] purposes except by involving additional parties.<ref>{{Cite web|url=http://www.iso.org/cms/render/live/en/sites/isoorg/contents/data/standard/04/47/44736.html|title=ISO/IEC 13888-2:2010 |website=ISO|language=en|access-date=2020-02-04}}</ref> See the [http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=44736 ISO/IEC 13888-2 standard].

Another application is to build [[hash function]]s from block ciphers. See [[one-way compression function]] for descriptions of several such methods.