Bletchley Park - where computers began
Bletchley Park, now the most famous code breaking facility in the world, but it was once one of Britain's best kept secrets. Here is where the German 'unbreakable' Enigma and Lorenz Cipher codes were secretly broken by a huge team of male and female code breakers led by Alan Turing and Gordon Welchman. Their work is said to have shortened World War II by two to four years.
This was also the site of the birth of computing with the mechanical Bombe machine used to break Enigma, and the world's first electronic, programmable computer the Colossus, which was used to break the Lorenz Cipher encryption which was used by Hitler himself. The Colossus was built by a relatively unknown man, even to this day, Tommy Flowers. |
Introduction: Encryption
Caesar Cipher
The Caesar Cipher is one of the earliest known ciphers. It was used by the Romans led by Julius Caesar to send secret messages.
It is a simple cipher compared to the ones used today, and just involves 'shifting' the alphabet so that the letters represent different ones. This shift is the encryption key. All ciphers need a key to unlock the hidden message. A shift of 1 (key=1) would mean that: 'A' = 'B' 'B' = 'C' 'C' = 'D' A shift of 3 (key=3) would mean: 'A' = 'D' 'B' = 'E' 'C' = 'F' |
Task 1Download the file here and print it off.
Write the alphabet around the large circle in black. Write the alphabet around the small circle in red. Enciphering: black to red Deciphering: red to black
Task 2Complete exercises 1 - 4
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Substitution Cipher
Task 3Complete exercises 5 - final activity
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A substitution cipher is when we don't have a standard shift. In this cipher, the coded alphabet can appear in any order. This makes the encryption a lot harder to crack. 26 different letters can be ordered in 403,291,461,126,605,635,584,000,000 different ways - exponential growth!
This is another example of exponential growth |