In modern cryptology, null encryption (or selecting null cipher or NONE cipher) is choosing not to use encryption in a system where various encryption options are offered, such as for testing/debugging, or authentication-only communication. Thus the text is the same before and after encryption. In mathematics such a function is known as the identity function. Examples of this are the "eNull" cipher suite in OpenSSL[1] and the "NULL Encryption Algorithm" in IPSec.[2]
