A Vigenère square

What you’ll need: A mind for mathematic patterns, and either a paper and pen or a fully functioning quantum computer (depending on what century you’re working in)

Songlist: A Badly Broken Code by Dessa, Box Full of Letters by Wilco

Further Reading: Decoded by Jay-Z

Ten years ago, while waiting for my plane at Heathrow Airport, I picked up a book called “The Code Book” by Simon Singh.  Now, I’m pretty good at solving the daily cryptoquip in my local paper*, so it was only logical to assume I’d make a good professional codebreaker.

I read the first chapter during my London to Minneapolis flight, a fascinating account of how Mary Queen of Scots was executed for treason based on the coded messages she sent from her prison cell.  Before diving into the next chapter, I flipped to the back of the book.  There, Singh had outlined the guidelines to a “cipher challenge,” a contest for which he would award £10,000 to the first person who cracked all ten codes Singh had created specially for this book.

Immediately, I took out a notebook and pen.  Stage 1: Simple Monoalphabetic Substitution Cipher.  Easy.  This was the kind of code I solved every day, the code employed by the cryptoquip, where one letter stands for another.  After scanning the page for a moment, I noticed the frequency of the letters JPX together and decided this must be THE; therefore J=T, P=H, and X=E.  It didn’t take too long to find other obvious clues, and before we’d crossed the Atlantic, I had the whole code solved, the keyword written down.  Naturally, I was pretty impressed with myself.  Here I was, a fourteen-year-old girl, already one-tenth of the way to £10,000, and I’d used no advanced technology.  I fell asleep, sure I would soon be a famous cryptanalyst.

At home, I began work on Stage 2: Caesar Shift Cipher.  Also fairly easy, because in this type of code you transpose the alphabet, then transpose it again, only shifted.  After trying out a few methods, I soon realized that the message had originally been written in Latin.  Oh, I get it: Caesar.  With this knowledge in hand, I completed Stage 2 with ease.  I went on to complete Stage 4: Vigenère Cipher, once known as le chiffre indéchiffrable, or the indecipherable cipher.  It was certainly more difficult, as it required a frequency analysis chart, the letters were not grouped into words, and it was in French.  Thus, once I solved the Vigenère, my pride was through the roof.  Unfortunately, Stage 4 was the last one that listed what type of code it was.  Stage 5 was just a bunch of numbers.  Stage 8 looked like this:

Simon Singh's Enigma encryption

After feeble attempts on some of these stages, I gave up.  I would not be a famous teenaged codebreaker after all.  I checked on the progress of the cipher challenge a few months later, and saw that all ten stages had, in fact, been solved.  The team that solved it, though, was a group of Swedish computer programmers/juggling enthusiasts who had a clear advantage over me (who knew that juggling is useful for code breaking?!)  Feeling a little better about my failure, I read Simon Singh’s description of the codes he’d created:

Stage 10 was intended to be the toughest public challenge cipher yet devised. Hence, I hoped that its cracking would help test the level of current codebreaking and perhaps stretch and encourage the development of algorithms.

Oh.  Oh, I see.  I failed because there was no possibility of success–I did not have a strong enough computer to contend with Singh’s code (he notes that he consulted with an encryption expert working for Microsoft for stages 9 and 10).  I still don’t and may never have the computer programming know-how to follow this dream, but man, am I good at those cryptoquips.

*Today’s cryptoquip solution: Whenever Obama’s vice president waits for the perfect moment to act, is he Biden his time?

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