Code of the Week!

view of the enigma machine

For your chance to win your very own signed copy of Simon Singh's Code Book try out your codebreaking skills with the "Code of the Week".

Solution for the "Code of the Week!" week starting 14th January 2008

Week 9 The Babbington Plot

To Anthony Babbington, I agree that you can murder Queen Elizabeth at the earliest time. From Mary.

Code of the Week 9 (week starting 14th January 2008)

The Babbington Plot

Mary Queen of Scots, the cousin of Queen Elizabeth I (Queen of England) was confined in prison Chartley Hall in Staffordshire in January 1586. With the plan to become Queen of England, Mary sent out coded messages to her code conspirator Anthony Babbington. These messages contained a secret plot to kill Queen Elizabeth I. These messages were intercepted by Queen Elizabeth's secret spy master Sir Francis Walsingham and using a mathematical technique known as Frequency Analysis the plot was revealed. As a result, Mary Queen of Scots was executed at Fotheringhay Castle in Northamptonshire on 8 February 1587.

Frequency analysis uses the knowledge of how frequently we use certain letters of the alphabet. For example, knowing that the most frequently used letter in English is 'e', you can then replace the letter or symbol used the most in the coded message with the letter 'e'. This can be done for the second most commonly used letter, third most, and so on.

More information on frequency analysis and a table showing the frequencies of each letter in the English alphabet may be found at: http://www.simonsingh.net/The_Black_Chamber/frequencyanalysis.html

The following note has been coded using the cipher actually used by Mary Queen of Scots.

Crack it to be in the running for this week's prize.



Some hints for you:

  • What are the most common symbols in the coded message? Perhaps they match the most common letters in English, which are E, T, A and N.

  • Can you guess any parts of the message? Who might it be to and who might it be from?

  • Focus on any 1-letter words. What words have only 1 letter?

  • Focus on any 3-lettter words. What are the common 3-letter words in English?

  • If you know the story of Mary, who might she talk about in the message?