Editing Null cipher (section)

== Usage ==
In general, it is difficult and time-consuming to produce covert texts that seem natural and would not raise suspicion, but a null cipher is an option if one is unable to use an advanced encryption method and has ample time. If no key or additional encryption is involved, the security of the message relies entirely on the secrecy of the concealment method. In the present day, null ciphers are used by prison inmates in an attempt to have their messages pass inspection.<ref name=fbi /><ref>{{Cite news|url=https://www.businessinsider.com/60-days-in-fbi-decrypt-secret-letter-2018-2|title=An Atlanta jail intercepted a letter from an inmate who was using a secret code to orchestrate a murder|first=Mark|last=Adabi|date=February 5, 2018|work=[[Business Insider]]|access-date=2018-09-30}}</ref>

Null ciphers are one of three major cipher types in classical cryptography (the other types being substitution and [[Transposition cipher|transposition]]), but they are less well known than the others.<ref name=":2" /> They are often marked as a subcategory of transposition ciphers,<ref name=":2" /> but that is not true, as transposition ciphers are scrambled messages.