Codebreaker 1

 Researching about different codes has been a bit of a refresher course for me. I love puzzles and working things out, and I really enjoy working out puzzles for mystery / unknown geocaches - some of the puzzles are ingenious, but quite often you have to be on the same wavelength as the puzzle setter. I remember watching a little snippet of Only Connect about 10 years ago and wondering what it was all about, as I really couldn’t work out what was going on. However, over time, we started watching it, and learnt about the way the game was played and we made the connections that enabled us to solved the puzzles. Admittedly, some of the connections are tenuous at times - and I wonder how on Earth anyone can see the connection in just one or two guesses.

Working things out and using logic to do so is a skill - it is something that can be learned. I was - and still am - in awe of people doing cryptic crosswords; my grandad used to do them, but I could never work them out. A teacher at school (when I was still teaching) used to do them, and during a week when teachers were encouraged to try new things in lunchtime and after school, he showed us some of the tricks for solving cryptic crosswords. In the past couple of years I have started doing them too - learning the words and phrases that are used to indicate what you need to do - e.g. upset in a crossword indicates an anagram.

First of all - let’s look at codes and ciphers; these two words do not mean the same thing. A code is where you substitute one word for another word or sentence - you generally need a code book or a crib sheet to help you. The idea of a code is to shorten the message. A cipher is where you mix up or substitute existing letters - it is an algorithm. Codes operate on semantics - on the meaning, whereas ciphers operate on the syntax - the symbols. What both codes and ciphers do is hide a message. 

I’ve looked at a number of different ciphers for the Codebreaker badge - and here are some of my findings.

Caesar cipher / shift - or ROT 13: the Caesar cipher shifts all letters a certain number of places, e.g. A becomes C, B becomes D, C becomes E - this is a shift of 2 letters, so is known as ROT 2 or rotation 2. A more common variant is ROT 13 - A becomes N, B becomes O, C becomes P - this is the only rotation that can be used to both encrypt and decrypt a message. Geocaching uses ROT 13 on its website for the clues. ROT 5 can also be found within geocaching - but this is generally used with digits, as it will both encrypt and decrypt the digits. Geocaching Toolbox is a great website for more information about all sorts of codes and ciphers - but this link is specifically about Caesar Shift.

Classic substitution is putting one letter in place of another - a bit like the code word puzzles, where you have a number to indicate a specific letter. 

Transposition ciphers could be thought of as a bit of Morecambe and Wise - all the same letters, just not necessarily in the same order! The letters don’t change, order of the letters within the message is scrambled according to some well-defined scheme - e.g. write every word backwards, or rail-fence cipher.

Vigenère cipher requires a square where each subsequent row is a Caesar shift of the original alphabet - it is known as a polyalphabetic cipher. A variation on this is the reverse Vigenère, where the alphabet goes backwards.

Book cipher is also known as the Ottendorf cipher; you have 3 numbers which correspond to page number, row number, and position of the word in the row. This is seen in the film National Treasure where they discover a secret cipher on the back of the Declaration of Independence. There is a problem with this cipher - you need to have the same copy / edition of the book - imagine the problems if you were using the bible, and one person had the King James Version, and another person was using The Message.

In researching all the different types of codes and ciphers I got to grips with how Playfair works and also how ADFGX works as well - these have been a bit of a mystery up until now.

The Enigma cipher is a very complex (to my mind) piece of engineering, which has an electromechanical rotor mechanism that scrambles the 26 letters of the alphabet. There are so many different aspects to this machine - a plugboard where letters could be exchanged with another letter, the ring setting of the rotor wheels - which indicated the position of each alphabet ring relative to its rotor wiring, the rotor orientation - setting the starting position for each rotor. In addition the machine had three (later four or five) rotors, and these all had different rotor wiring and had to be in a specific order. To be able to decrypt messages from an Enigma you need a list of daily key settings (amongst other things) so that you had: wheel order, ring settings, plug connections, (wiring of reconfigurable deflector - which came in later versions) and the starting position of the rotors. If you had this information you could use another Enigma machine to decrypt the message. This cipher is nigh-on impossible to break without other clues; something that helped is that no letter can be enciphered as itself. The film Enigma (starring Kate Winslet and Dougray Scott) is great at explaining how the Enigma machine works, and how they could use other bits of information to get the code settings for the day.

Some ciphers - such as Classic Substitution ciphers can be broken by using frequency analysis. You look at how often certain letters appear, and compare this with how often certain letters appear in plaintext. Think of the Scrabble tiles - less coming letters have a higher value in Scrabble, so the lower value letter tiles are the more common letters. In English common letters (in no particular order) are E, A, T, N, S, I, O, R - and using this information you can start to work out possible words - especially if you have an idea about the content of the message. This knowledge of letter frequency is useful for the word games that have become popular this year - Wordle, Bardle, Quordle. I use the same 2 starting words each time with these game - PIOUS and EARNT (I have to use EARTH for Bardle, as the bard didn’t use EARNT in his works). In this way I have covered all the vowles and some of the most common consonants, and then it is a matter of working out anagrams!