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BOSS Library

The effective BOSS operative has a wide range of skills. Alongside a selection of Harry’s favourite books about codebreaking, we have included the GCHQ and Bletchley Park puzzle manuals to train your mind, and a selection of novels, biographies, and history books that will help you to learn the important techniques of spy craft.

If you want something to listen to while browsing, then here is something written for the National Cipher Challenge back in 2003. If you fancy writing and recording your own Cipher Challenge theme send us a link. You never know, we might add it here!

Harry’s Theme by Ray d’Inverno

Christmas Miscellany

It is an old tradition to produce a Christmas Almanac, or Miscellany, and while we make no great claims to originality we thought it would be worth joining in the fun. Some of the items below were suggested by competitors or long-time cipher challenge community members. Others are curiosities from Harry’s bookshelves. we hope you find something to enjoy here. Merry Christmas!

If you have your own suggestions for something we should add, why not let us know in the forum?

Madness suggested these pages on the Nihilist cipher

Absolutely nothing to do with codebreaking, but we love Cabin Pressure and we think you might enjoy the famous Christmas special! And if you want something more mathematical, you can always try the Logician’s Common room sketch!

Fancy some Christmas reading? How about the official 1950 Army field manual on cryptography, now declassified.

We added this pdf of Gaines’ book for the Christmas offering last year and we think a lot of you made good use of it. This year Madness has produced an errata for it, and we hope that Helen would not mind us publishing that here alongside her marvellous book.

If you like Sudoku, then we think you will love this! It was described as one of the best, by the amazing Cracking They Cryptic Team. We suggest you give it a go!

The Guardian have been publishing the King William’s College Quiz for years. It is devilishly difficult, but we have a feeling that the cipher challenge community might actually be quite good at “devilishly difficult things, so have at it!

In the completed puzzle the numbers 0 through 9 appear in each of the top six rows of the grid so that they give the column sums at the bottom and no number appears in twice in adjacent cells, including diagonal adjacency.

Some of you may remember this from 2020. The Letter Wriggler kindly wrote a series of grid puzzles for us, and this was one of the harder ones.

2023 – A whole year of mathematics on one page!

Quanta is one of our favourite magazines and in this article they review Maths in 2023.

2023 The Year of Machine Learning

2023 was the year that AI broke through to the public, and it even had an impact on the Cipher Challenge. (The poster was a collaboration between Harry and Midjourney.) While it is rather technical, you might want to take a look at this article written about the mathematics behind deep neural networks, commissioned for the 2022 International Congress of Mathematicians.

Alex Rider is back – and playing a deadly game

Anthony Horowitz is a fan of the National Cipher Challenge and has supported us for a while now. This year he has kindly offered a free copy of his latest Alex Rider novel as a prize in a random draw from the first 1,000 registrations. To enter, just register at the login page. If you are the lucky winner we will let you know using the BOSS messaging system.

When his best friend Tom is abducted, Alex Rider is given an ultimatum by Nightshade – a sinister cult of assassins with a score to settle. But what twisted evil are they planning? And how is it connected to a revolutionary new gaming system? With no idea who to trust, Alex finds himself dragged into a nightmare world – where nothing is real, but the game could kill you. 

Nightshade Revenge, the 14th Alex Rider mission in the No.1 bestselling series, is out 7th September 2023, read an exclusive extract here, and read the Book Brothers’ review here.

One of my own favourite introductions to classical cryptography is Helen Gaines’ “Cryptanalysis”, which is now out of copyright, and you can download a copy here.

In the introduction Helen lists several other classics that inspired her, and for your entertainment, the Elves have tracked them down online. You can find them below.

The Non-Fiction Section

Greatest Hits

If you are a complete beginner to codebreaking then you should probably start with Harry’s guide to codebreaking, written for the National Cipher Challenge. You can download the pdf here. Of course there are a number of other excellent books about code breaking and we have listed some here for you to explore. You should be able to order them through your library, but we have linked to Amazon so you can read more about them.


The Code Book by Simon Singh
the Cracking Book by Simon Singh
Can You Crack the Code by Ella Schwartz
Cryptography for Dummies by Chey Cobb
DECIPHER: The Greatest Codes Ever Invented and How to Break Them by Mark Frary
Elementary Cryptanalysis by Abraham Sinkov

Deep Cuts

A Very Short Introduction to Cryptography by Fred Piper and Sean Murphy
Cryptanalysis a study of ciphers and their solutions by Helen Fouché Gaines
Mathematical Ciphers: From Caesar to RSA by Alan L. Young
A link to a website dedicated to preserving the historic archive of cryptograms originally published in Flynn's and edited by E.M Chavez
A link to an online copy of "The Military Cipher of Commandant Bazeries by Rosario Candela.
A link to an online version of the "Manual for the Solution of Military Ciphers" by Parker Hitt


The GCHQ Puzzle Book
The GCHQ Puzzle Book II
Bletchley Park Brainteasers by Sinclair McKay
Secret Codes and Cryptogramsby Elena Dunin
Puzzles for Spies by GCHQ

The Trailblazers

In Code by Sarah Flannery
The Man Who Knew Too Much by David Leavitt
The Woman Who Smashed Codes by Jason Paggone
The Secrets of Station X by Michael Smith
The Man Who Broke Napoleon's Codes by Mark Urban

The Technical Section

From time to time BOSS staff produce guides that you might find helpful. Some of these are short notes, others expand to considerably longer textbooks. They are free for you to download and read as part of the competition, but copyright remains with the authors.

The Fiction Section

Anthony Horowitz with his book "Moonflower Murders", the outstanding sequel to "The Magpie Murders"
Anthony Horowitz with his book Moonflower Murders

We asked Anthony Horowitz for his three favourite books containing ciphers. His nominations were fantastic and we couldn’t agree with them more:

The Adventure of the Dancing Men by Sir Arthur Conan Coyle
The Secret of the Unicorn by Hergé
Red Rackham's Treasure by Hergé
Moriarty by Anthony Horowitz

Of course, if you want more Horowitz there is plenty to keep you entertained! On TV you have Midsomer Murders, Alex Rider and Foyle’s War to binge on, or a choice of so many books we couldn’t list them all! Here is a selection to get you started.

The Word is Murder by Anthony Horowitz
Anthony Horowitz himself, and his sidekick(?) Hawthorne
Magpie Murders by Anthony Horowitz
One of the strangest murder mysteries you will ever read!
The Falcon's Malteser by Anthony Horowitz
The first novel in the hilarious Diamond Brothers series
Trigger Mortis by Anthony Horowitz
Bond is reborn

Back in 2020, in the middle of lockdown, we were delighted to welcome the Book Brothers as guest librarians at BOSS. You may already follow thm on Twitter, and know that they have a huge fanbase including a number of famous authors. We asked them to recommend some new books for our list and this is what they came up with

The Adventures of John Blake by Philip Pullman

A beautiful graphic novel by Philip Pullman. Read the Book Brothers review here:

Another great graphic novel that is also an excellent movie. It tells you the story of Alan Turing, the brains behind the invention of the modern universal computer.

Part of a fantastic series, you can reviews of this one and of the companion, The Hunt for the Feathered God, here

Another exciting series, this one by James Dashner, with four volumes.

James Bond never had much time for breaking codes, but several of his adventures involved ciphers or cipher machines. The novels are a bit dated now, but Charlie Higson updated them brilliantly by taking us back to Bond’s early years. Definitely worth a look.

It has been a long time since they published a new Alex Rider novel, and it seemed just perfect that the latest volume came out the same day the Special Edition Cipher Challenge launched back in March. As AH tweeted, “Alex Rider loves codes and ciphers!”

The Book Brothers are also big fans. For those who enjoy AH’s twisted sense of humour (which was also evident in his TV series Midsomer Murders) you might like to try his Diamond Brothers series. The Book Brothers reviewed The Falcon’s Malteser, and as an extra special treat, AH has made a new story, Where Seagulls Dare, freely available to keep us all amused during the lockdown.

Holly Jackson took thrillers to a new place and redefined the phrase “Good Girl” with her cracking trilogy.

The first novel in the "Good Girl's Guide to Murder" series by Holly Jackson
The second novel, "Bad Blood", in the "Good Girl's Guide to Murder" series by Holly Jackson
The third novel, "As Good as it Gets", in the "Good Girl's Guide to Murder" series by Holly Jackson

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