Letter sent by Mary Queen of Scots to her co-conspirator Anthony Babington.
Unfortunately for Mary, there is a very simple way of cracking this code that doesn't involve trial and error, but which does Mary wanted to kill Elizabeth so that she herself could become Queen of England and was sending coded messages of this sort to her co-conspirator Anthony Babington. This type of code was used by Mary Queen of Scots when she was plotting against Elizabeth the First. There are 400 million billion billion possible combinations! It would take the enemy far too long to figure out what letter of the alphabet each symbol stood for just by trying all the possibleĬombinations of letters and symbols. For a long time, people thought this type of code would be really hard to crack. Instead of an 'A' we could write *, instead of a 'B' write + etc. So, what about coding messages another way? Instead of writing a letter, we could write a symbol, or draw a picture. An enemy code breaker would only have to try out 25 different possible shifts before they were able to read your messages, which means that your messages wouldn't be secret for very It can easily be done just by trial and error.
If you've got the hang of coding messages by shifting the alphabet forward, then you might have realised that it is actually pretty simple to crack this type of code. If your letters are numbers and encoding is addition, then decoding is subtraction, so if you've coded a message by adding 5, you will have to decode the message by Then have a go at coding your name by shifting the alphabet forward by more places by adding greater numbers eg adding 5, then adding 10. Have a go at coding your name by adding 3 to every letter. In maths we call this 'MOD 26', instead of writing 26, we go back to 0. However, you do have to be careful when you get to the end of the alphabet, because there is no letter number 26, so you have to go back to number 0. Then encoding, shifting the alphabet forward three places, is the same as adding three to your starting number: Aįor example, encoding the letter 'A' is 0+3=3, which is a 'D'.
So where's the maths? The maths comes if you think of the letters as numbers from 0 to 25 with A being 0, B being 1, C being 2 etc. This all seems very clever, but so far it's all been letters and no numbers. Have a go at trying to work out these messages which could have been sent by Caesar or his generals: When Caesar's generals came to decipher the messages, they knew that all they had to do was go back three places in the alphabet. When he got to the end of the alphabet, however, he would have to go right back to the beginning, so instead of an 'X', he would write an 'A', instead of a 'Y', he'd write a 'B' and instead of 'Z', he'd write a 'C'.Ĭomplete the table to find out how Caesar would encode the following message: Caesar's message Instead of a 'B', he would write an 'E', instead of a 'C', he would write an 'F' and so on. Instead of writing the letter 'A', he would write the letter thatĬomes three places further on in the alphabet, the letter 'D'. So Caesar would write messages to his generals in code. He needed a way of communicating his battle plans and tactics to everyone on his side without the enemy finding out. Nearly 2000 years ago, Julius Caesar was busy taking over the world, invading countries to increase the size of the Roman Empire. In fact, some of the most famous code breakers in history have been mathematicians who have been able to use quite simple maths to uncovered plots, identify traitors and influence battles. But you should.Ĭracking codes and unravelling the true meaning of secret messages involves loads of maths, from simple addition and subtraction, to data handling and logical thinking.
You probably wouldn't think of mathematics. When you think of spies and secret agents, you might think of lots of things nifty gadgets, foreign travel, dangerous missiles, fast cars and being shaken but not stirred.