Editing Book cipher (section)

== Security ==
Essentially, the code version of a "book cipher" is just like any other code, but one in which the trouble of preparing and distributing the [[codebook]] has been eliminated by using an existing text. However this means, as well as being attacked by all the usual means employed against other codes or ciphers, partial solutions may help the [[cryptanalysis|cryptanalyst]] to guess other codewords, or even to break the code completely by identifying the key text. This is, however, not the only way a book cipher may be broken. It is still susceptible to other methods of cryptanalysis, and as such is quite easily broken, even without sophisticated means, without the cryptanalyst having any idea to what book the cipher is keyed.<ref>{{Cite book |last=Yardley |first=Herbert O. |url=https://archive.org/details/americanblackcha00yard/page/n3/mode/2up |title=The American Black Chamber |publisher=[[Ballantine Books]] |year=1981 |isbn=0-345-29867-5 |location=New York |access-date=2023-02-13 |orig-date=1931 |url-access=registration}}<!--There's a diagram he uses to help explain how it's done. A professional could break a book cypher in a matter of hours.--></ref>{{page needed|date=April 2011}}