Alan Turing and Code Breaking Back to the Future – Lesson 1

Starter – on whiteboards Can you think of any famous figures in the world of computing? What did they do? Discuss with a partner and be ready to share with the rest of the group.

Learning Objectives Learning Objectives Success Criteria To understand who Alan Turing was To understand how messages can be encrypted using ciphers. To understand how to use a cipher key to decipher codes Success Criteria To discuss the importance of Alan Turing To use logical thought to crack codes using a variety of different ciphers Literacy – Key Words Cipher A Cipher is a ‘Secret Message’ often written in code Decipher A method to unscramble a cipher so that the ‘Secret Message’ can be understood Encryption A method used to scramble messages so that if they are intercepted they cannot be read / understood

Learning Habits Reasoning: Noticing details Adapting : Thinking rigorously, methodically and giving explanations. Noticing details Adapting : Reflecting and making changes Empathising… …with feelings and views Effective use of time Questioning: Asking questions to get below the surface Listening… …to understand Imagining… …how things could be and seeing a range of possibilities Distilling… …what you have learnt and what you need to learn Collaboration: Working effectively with others Meta Learning: Talking about how you have been learning Imitation: Picking up good habits from others Independence: Working effectively alone Managing distractions… …and sustaining concentration Capitalising: Using resources purposefully Making links… …and recognising relevance Perseverance: Overcoming frustration and difficulty Planning… …your learning in advance

What do we already know? Who was Alan Turing?

Setting the Scene The world was at war, Britain were fighting the Nazis German soldiers / government were sending messages to each other in order to communicate strategies. British Intelligence were managing to intercept these messages – but they were encrypted... …But if there was a way to decrypt / decipher the messages, then Britain could get vital information about their enemy! Therefore information / intelligence could be a vital tool in the war!

Bletchley Park Bletchley park was an office set up by ‘British Intelligence’ to try to crack the code so that these messages could be understood. …and this is were Alan Turing’s story begins!

Alan Turing Alan Turing played a vital role in deciphering the messages encrypted by the German Enigma machine, which provided vital intelligence for the Allies. He took the lead in a team that designed a machine known as the ‘bombe’ that successfully decoded German messages. He became a well-known and rather eccentric figure at Bletchley.

The Enigma This is the machine that the Germans invented to write their encrypted messages. The machine was electric and each time a key was pressed it would turn a series of rotors. These rotors alter the letter pressed so that messages would be scrambled. The different rotors meant that the encryption machine could be set up one of 100,000 different ways. So each day, the ‘Enigma’ would be set up slightly differently making it hard for anyone to decrypt, unless they had the key (if, in other words, they knew how it had been set up that day).

The Bombe Machine Turing invented this machine – the Bombe. Messages could be fed into it and the machine could help ‘pin point’ the way that the Enigma was set up when writing that particular message. With this information, British Intelligence could get to work trying to decrypt the messages allowing the British to learn many German secrets. Many of which were instrumental in the War being won!

Alan Turning – A sad end to an amazing man Sadly, Alan was persecuted for his homosexuality. In the 50’s he faced prison or daily injections to help supress his feelings. He chose the injection. A short time later he committed suicide. Terrible treatment of an amazing man who played a massive part in winning the war and saving us from Nazi rule.

Who was Alan Turing? Mathematician / One of the first Computer Scientists Created a machine that could help decipher messages sent by the German encryption machine called ‘the Enigma’. Out of the 100,000 different ways the Enigma could be set up to encrypt messages, the Bombe (Turing’s invention) could reduce these possibilities by working out how the Enigma was set up for each message received. British Itelligence could therefore decipher the messages much faster, understanding the enemy’s next move and help win the war!

Lets Crack Some Code! We will now exercise some of the logic that Turing used when cracking German messages.

Activity – Cracking Code PigPen Ciphers What is this message?

Pig Pen Ciphers - How they work This is the KEY By locating the letters in the key, you can identify the symbols which replace the letter. To make it harder, the letters can be in different positions to these, so a symbol in one message might represent a different letter in another…without the key it would be very hard to decrypt.

Activity Complete one of two worksheets Levels 3-5 Worksheet

Plenary Who was Alan Turing? Why do we need to encrypt messages? What do we need to decrypt a message?