Encryption January 29th and 30th

Encryption

This lesson and next lesson we are going to explore encryption in more detail:

Task 1

Make sure that you have the following definition

A  key is used to encrypt plain text into meaningless cipher text, the same key is used to decrypt the data back into its original form. Only someone who knows the key can decrypt the cipher. If you don’t have the key you need to crack the code.

Task 2

Watch the following film about the Enigma machine.  Afterwards in your own words try to write a summary of how it works.

Use the YouTube video ‘158,962,555,217,826,360,000’ to introduce the Enigma machine: http://www.youtube.com/watch?v=G2_Q9FoD-oQ

Task 3

Introduce the Codebreaker challenge: http://turinggame.sciencemuseum.org.uk. Pupils to work in pairs to tackle the challenge.

Homework:  Last week you created a Caesar Cipher.  Your task this week is to create your own cipher.   You will need to show how it works.  It must be secure but also you must show how to translate the enciphered text back into plain text. This can be done in 

Post your answers to the blog by Thursday 5^th February at 5.00pm

Task 4

First of all let’s look at the following video about the Caesar Cipher.  Make sure that you have a short description of how the Caesar Cipher works.

http://www.youtube.com/watch?v=sMOZf4GN3oc.

Try to send some messages to your partner using the Caesar Cipher

TASK 5

Use a Caesar cipher to decode and encode these messages.
Plain text	Shift	Encrypted text
THE ENIGMA MACHINE WAS INVENTED BY THE GERMANS	+3
COLOSSUS WAS THE WORLD’S FIRST DIGITAL COMPUTER	+4
	+5	YMJ HFJXFW HNUMJW NX FS JCFRUQJ TK WTRFS NSLJSZNYD
	-3	QEB HBV FP EFAABK RKABO QEB CILTBO MLQ

Task 6

With a partner, produce a step-by-step guide to using a Caesar cipher to produce an encoded message.

Task 7

Produce a step-by-step guide to decrypting messages that have been encoded using a Caesar cipher.