Alan Turing and Ciphers Computer Science and LGBT

Lesson Aims To learn about one of the most famous LGBT people in Computing History To create a cipher program to code words KEYWORDS LGBT = Cipher = Encryption = © Educate & Celebrate 2005 -2018 All rights reserved

Decode the sentence Using the sheet provided, work out the sentences…. Answer Alan Turing created a computer which helped break the Nazi enigma code during World War 2. He is seen as the father of modern computing. © Educate & Celebrate 2005 -2018 All rights reserved

Creating your own secret message You are going to create a program to create your own secret messages This is known as the Caesar Cipher and was used by the Roman emperor to send messages. Just move each letter of the alphabet a certain number along. © Educate & Celebrate 2005 -2018 All rights reserved

Setting up the Shift Click on green flag to Start algorithm running Display output of Caesar Cipher message Create variable ‘Shift’ = how many letters will be shifted across. Set Shift to start at 0 Get value for Shift by asking for Input Checking shift is within alphabet eg -25 to 25 Error message output if not in range Set Shift to what was input © Educate & Celebrate 2005 -2018 All rights reserved

Inputting the message Create a variable ‘alpha’ to store whole alphabet Ask for input of message Create variable ‘message’ to = the input Create a variable ‘output’ and set it to be blank Create a ‘count’ variable and set to 1 to go through each letter of message © Educate & Celebrate 2005 -2018 All rights reserved

Creating the Cipher © Educate & Celebrate 2005 -2018 All rights reserved A loop to make the swap happen the length of the message Variable ‘Swapped’ set to false to ensure all letters are swapped Variable ‘ch’ = to be the letter you have reached in the message Variable i to be first letter to be looked at Loop until all letters swapped If the first letter is the one to change then Variable ‘index’ is that letter shifted up to 26 Output is the new shifted letter The swap has been made Move on from i to next letter If Swapped has not happened Output is original letter Count through each letter until length of message reached Display the encrypted message for 5 second Stop the algorithm

Create the Scratch program • Use sheet to help you create the program. • Get another student to test it! Extension: What number in the shift would you need to use to decipher the message? © Educate & Celebrate 2005 -2018 All rights reserved

Now for something harder… The Enigma Machine This had 150, 000, 000 different combinations (150 million) which changed EVERY DAY Alan Turing – was able to design a computer which actually solved the codes on this machine which meant the Allies knew what the Germans were planning and so was vital in helping the stop them taking over Europe © Educate & Celebrate 2005 -2018 All rights reserved

A bit more about Alan Turing He was born in London in 1912, and studied maths at King’s College Cambridge. Turing’s mathematical work around algorithms is used today in computing, and so he is seen as the father of technology. During WWII he worked at Bletchley Park, as part of the team trying to crack the German Enigma code. After the war he was secretly awarded an OBE for his work in breaking the Enigma code. In 1952, after a burglary at his home, detectives initially thought that Turing was a spy. When investigating him, they discovered he had been in a relationship with a man. As homosexuality was illegal, Turing was charged with “gross indecency” and was given a choice between imprisonment or probation, which included hormone treatment to “lower his libido”. On June 8 th, 1954, Alan Turing was found dead by his housekeeper. The cause of death was suicide by cyanide poisoning. In 2014, as a result of a petition from the public, the Queen officially pardoned Turing, and the government issued an apology for his conviction. © Educate & Celebrate 2005 -2018 All rights reserved

Plenary • What have you learnt about making your own cipher? • What have you learnt about the experience of some LGBT people like Alan Turing before the legalisation of homosexuality in 1967? • 63 years after his conviction, Alan Turing’s family marched in the 2015 London Pride Parade. How do you think Turing’s life would have been improved if he had lived in 2015 England? © Educate & Celebrate 2005 -2018 All rights reserved