KS3 Science & Maths - Breaking News!: Code Breaking

Clever mathematical methods are responsible for keeping data safe and private - even your private email!

• How did mathematicians help win the war?

• Why is 2012 a special year for Bletchley Park?

• Is any communication secret?

• Are any of my personal details private on the internet?

• How is prime factor decomposition related to cryptography?

   - What is public key cryptography?

   - What about elliptic curves?

• What is frequency analysis and how can it help crack a code?

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(Source of video: youtube)

Breaking Germany's Enigma Code - BBC History

   During the Second World War, Bletchley Park was the site of the United Kingdom's main decryption establishment, the Government Code and Cypher School (GC&CS), where ciphers and codes of several Axis countries were decrypted, most importantly the ciphers generated by the German Enigma and Lorenz machines.

A guided Virtual Tour of Bletchley Park

   Cryptography is the study of secret codes. Prime Factorization is very important to people who try to make (or break) secret codes based on numbers. That is because factoring very large numbers is very hard, and can take computers a long time to do.

 Explore the RSA algorithm to find out how it works.

 Encrypted text is sometimes achieved by replacing one letter by another. Instead of writing a letter, we could write a symbol, or draw a picture. The weakness of this method is that although the letters themselves change, their frequency does not. So, any enthusiastic cryptographer could crack the code using frequency analysis tables of the original plain text language.

   The method of decryption using frequency analysis has two stages:

   1.Work out the frequencies of letters or symbols in the ciphertext and compare the results to the letter frequencies in the language: e.g., we know "e" is the most common letter in English, and "the" is the most frequent word.

   2.Make intelligent guesses for words or letters: e.g., a lone letter in English will be "I" or "A". This method is time consuming, and is less accurate for short messages, but is a valuable aid to the cryptographer.

You can try out some code breaking examples in the Young Codebreakers' Zone!