History Main / TheBookCipher

* One episode of ''{{WesternAnimation/Cyberchase}}'' used this, using a cookbook with the page-line-word code. Once the main characters find out that Hacker has a copy of the book and is using it to decode their messages, they quickly come up with a new code. Clueless Hacker still thinks the code is the same when he intercepts the new message.

* In ''Literature/TheValleyOfFear'', SherlockHolmes decrypts a message enciphered with a book cipher by deducing which book had been used as a key text.

Big and well-known books make better sources as you have more words to choose from (thus Literature/TheBible is often the source), and no one will react if you're walking around with a pocket version of ''Literature/TheDaVinciCode''. Relatedly, if you are unfortunate enough to lose your copy, a well-known book will be easier to replace without raising eyebrows. If you're walking around with an 1824 edition of a book, or asking specifically to buy a copy of the fourth printing of the second edition of something... people may well get suspicious (especially the detective who's after you). Of course, using a widely available book also makes it easier for other people to read your messages, should they be intercepted, and while the book itself may be utterly innocuous, sending a letter that is merely a long list of numbers is an unmistakeable indication that you are communicating in code.

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* GrahamGreene's heroes often use book codes. In ''The Human Factor'', several books are used, and an edition of Charles Lamb's ''Tales from Shakespeare'' is used in ''Our Man in Havana''.

* The German spy uses this kind of encryption in ''[[Literature/ErastFandorin The Death of Achilles]]''.

* The heroes of the MatthewReilly novel ''Six Sacred Stones'' used a book cipher to send confidential messages to each other. The key text was [[spoiler:the Harry Potter books]], but the messages were sent via [[spoiler:a Lord of the Rings forum to make the key text harder to identify]].

* In ''A Presumption of Death'', LordPeterWimsey, on assignment for British Intelligence in WWII Nazi-occupied Europe, uses a code based on the works of Creator/JohnDonne. The Germans, suspecting that an intelligence service in which Oxonians have a major role would choose a classical work of English literature, systematically try such works until hitting the right one and breaking the code, coming near to catching the spy. Wimsey then improvises a new code, based on an unpublished text known only to himself and his wife.

Big and well-known books make better sources as you have more words to choose from (thus Literature/TheBible is often the source), and no one will react if you're walking around with a pocket version of ''TheDaVinciCode''. Relatedly, if you are unfortunate enough to lose your copy, a well-known book will be easier to replace without raising eyebrows. If you're walking around with an 1824 edition of a book, or asking specifically to buy a copy of the fourth printing of the second edition of something... people may well get suspicious (especially the detective who's after you). Of course, using a widely available book also makes it easier for other people to read your messages, should they be intercepted, and while the book itself may be utterly innocuous, sending a letter that is merely a long list of numbers is an unmistakeable indication that you are communicating in code.

* A book cipher plays an important role in the TV version of ''{{Sharpe}}'s Sword''. The key text is [[spoiler:Voltaire's ''{{Candide}}'']].

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* Used in ''[[Literature/TheGoodSoldierSvejk The Adventures of Good Soldier Svejk in the World War I]]'' when the officers are briefed on the newest cipher method, which apparently is a variant of the book cipher based upon the pages 160 and 161 of a German novel "''Die Sünden der Väter''". However, the book used is a novel in two volumes and [[TheFool the protagonist]], when ordered to deliver them to the battalion officers, was not informed that it was the second part which was needed and delivered the first tomes only, keeping the second volumes in storage, believing that 'they gentlemen officers would surely like to read the novel in the proper order, as anyone else, and after they had read the first part they'd be issued with the second part'. {{Hilarity ensued}} during the briefing, when only ([[HighHopesZeroTalent overly ambitious yet generally incompetent]]) officer-cadet Biegler was [[TooDumbToFool brave enough to point out]] that the example given does not make any sense, while other officers just kept calm and quietly assumed that their regimental colonel finally went completely bananas and would be soon [[KickedUpstairs promoted to the war ministry]].

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* This is described and used in ''[[Literature/{{Chalion}} The Curse Of Chalion]]'' by LoisMcMasterBujold. In a culture in which printing is a relatively recent invention, there aren't many true duplicates, but the characters manage to turn up identical copies of a heavy theological tome.

* In the Season 2 finale of BBC's ''Series/{{Luther}}'', the numbers in a notebook is revealed to be this. This gives the police an OhCrap moment when the suspect's RoomFullOfCrazy turns out to be [[NeedleInAStackOfNeedles full of books]]. [[spoiler:But as any book used must not only be the same title, but also the same edition, Luther realises this collection of secondhand books can't be the one used for the cipher. It's a Gideon's bible that the killers could find in any hotel room if needed.]]

* A different version occurs in ''Series/PersonOfInterest'', where the Machine sends a list of numbers and letters that correspond to the Dewey classification of the books in Finch's library.

* This is described and used in ''[[Literature/{{Chalion}} The Curse Of Chalion]]'' by LoisMcMasterBujold.

Big and well-known books make better sources as you have more words to choose from (thus Literature/TheBible is often the source), and no one will react if you're walking around with a pocket version of "TheDaVinciCode". Relatedly, if you are unfortunate enough to lose your copy, a well-known book will be easier to replace without raising eyebrows. If you're walking around with an 1824 edition of a book, or asking specifically to buy a copy of the fourth printing of the second edition of something... people may well get suspicious (especially the detective who's after you). Of course, using a widely available book also makes it easier for other people to read your messages, should they be intercepted, and while the book itself may be utterly innocuous, sending a letter that is merely a long list of numbers is an unmistakeable indication that you are communicating in code.

* Used in [[TheGoodSoldierSvejk The Adventures of Good Soldier Svejk in the World War I]] when the officers are briefed on the newest cipher method, which apparently is a variant of the book cipher based upon the pages 160 and 161 of a German novel "''Die Sünden der Väter''". However, the book used is a novel in two volumes and [[TheFool the protagonist]], when ordered to deliver them to the battalion officers, was not informed that it was the second part which was needed and delivered the first tomes only, keeping the second volumes in storage, believing that 'they gentlemen officers would surely like to read the novel in the proper order, as anyone else, and after they had read the first part they'd be issued with the second part'. {{Hilarity ensued}} during the briefing, when only ([[HighHopesZeroTalent overly ambitious yet generally incompetent]]) officer-cadet Biegler was [[TooDumbToFool brave enough to point out]] that the example given does not make any sense, while other officers just kept calm and quietly assumed that their regimental colonel finally went completely bananas and would be soon [[KickedUpstairs promoted to the war ministry]].

* In the film ''Film/{{Unknown}}'', Prof. Bressler's [[spoiler:passwords]] are obscured by an Ottendorf cipher.

* In the Season 2 finale of BBC's ''{{Luther}}'', the numbers in a notebook is revealed to be this. This gives the police an OhCrap moment when the suspect's RoomFullOfCrazy turns out to be [[NeedleInAStackOfNeedles full of books]]. [[spoiler:But as any book used must not only be the same title, but also the same edition, Luther realises this collection of secondhand books can't be the one used for the cipher. It's a Gideon's bible that the killers could find in any hotel room if needed.]]

* A different version occurs in ''PersonOfInterest'', where the Machine sends a list of numbers and letters that correspond to the Dewey classification of the books in Finch's library.
* A variation in an episode of ''MurderSheWrote'' set in Russia. One of the clues in the Murder of the Week was a manuscript about Soviet politics, beginning with the sentence, "The first and last word on the fate of Lenin was always in the hands of the Soviet people." After noticing a number of glaring grammatical errors, Jessica Fletcher realized that the first sentence was the key to the code; the first and last words on each page, read consecutively, revealed the identity of a Soviet official who turned traitor.

* In the second episode of Creator/TheBBC's ''Series/{{Sherlock}}'', they encounter a number [[spoiler:of symbols]]. This turns out to be [[spoiler:numbers written in an ancient Chinese script, with the book being a Tour Guide of London (which ends up as part of Fridge Brilliance, as the Chinese Gang use these symbols to arrange meeting points]].

* In the second episode of TheBBC's ''Series/{{Sherlock}}'', they encounter a number [[spoiler:of symbols]]. This turns out to be [[spoiler:numbers written in an ancient Chinese script, with the book being a Tour Guide of London (which ends up as part of Fridge Brilliance, as the Chinese Gang use these symbols to arrange meeting points]].

* ''Series/{{Wiseguy}}'' does a different version whenever the protagonist, undercover cop Vinnie Terranova, wants to pass on information to [[Lifeguard MissionControl]]. He gives an authentication code consisting of words taken from that day's newspaper.