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Encryption Decryption Teacher Resource

Welcome to the Maker Project Encryption Decryption Virtual Excursion. In this session, your students will gain the tools for basic cryptology, understand how these concepts relate to modern encryption techniques and how encryption effects their personal information, privacy, and how they can keep their information more secure online.

Included in this document are extension activities to follow up after the session to help maximise your students’ learning from our Virtual Excursion.

What to expect

During the Virtual Excursion we will look at the development of cryptology through the story of its innovation, building students understanding through making, using and cracking some historical cyphers. With this new knowledge in mind we will also look at modern encryption in the online age.

Runtime: 60 minutes

Time

Segment Description

Teacher Notes

5 – 10 min BEFORE

Audio Visual Check

Teacher to adjust video conference camera and microphone to ensure the whole class is visible and audible

We will be asking questions throughout the session

0-5 min

Introduction & studio tour:

 

What is encryption?

We will do a tour of the studio and show how we use the green screen. We will be asking students to say what they think encryption is and where it is used. We will also define some terms

Teacher to facilitate answering of questions

5-20 min

Caesar cypher

Activity: encrypt a message (10mins)

 

After explaining how the Caesar cypher works, each student will encode their own secret message

Teacher to hand out cypher wheels and facilitate the encryption of messages, make sure students’ messages are not longer than 5-8 words long

20-35 min

Deciphering encryption

Activity: how to crack encryption

After explaining how to crack the encryptions, students randomly get given another student’s secret message and are required to break it

Teachers to collect up all secret messages and randomly hand them all back out. Teachers to also facilitate the deciphering process

35-40 min

Polyalphabetic cyphers

Activity: Use Vignere Cypher

Vignere Cypher is introduced and students have to encrypt the words HELLO HELLO

Teacher to assist facilitation by picking students to help with discussion and helping students with the activity

40-45 min

Enigma Machine

Look at the history of the enigma machine

Teacher to assist facilitation by picking students to help with discussion

45-50 min

Modern encryption

 

RSA public key encryption introduced here, major advance for internet security

Teacher to assist facilitation by picking students to help with discussion

50-58min

Password activity

Activity: classroom brainstorm

Here we cover password security and how encryption relates to it

Teacher to facilitate discussion and brain storming of common passwords and passwords students think will be strong

58-60 min

Reflection and Conclusion

No action required

 

 

Information to assist facilitated activity

Materials required for session

Caesar cypher wheel and Vigenère cypher table (1 per student) See appendix

A4 paper sheets (2 per student)

Safety considerations

N/A

Tips and Tricks

Try to become familiar with the various cyphers before the workshop as this will make facilitation much easier.

Caesar cypher is an easy one and you’ll pick it up quickly. This video explains how it works https://www.youtube.com/watch?v=sMOZf4GN3oc the cypher wheel we will send out allows different shifts to be found quickly.

Vigenère cypher is a little more complex – it is worth having a bit of a look at before the workshop in order to become acquainted with it. This video explains how to use a Vigenère table to encrypt a message - you can stop watching at around the 1:40 mark https://www.youtube.com/watch?v=47BHvzLdPxw

RSA cypher we only examine conceptually but it is worth understanding the significance of public and private keys before-hand as students may have questions after the workshop. This is a good explanation for public and private keys https://www.youtube.com/watch?v=GSIDS_lvRv4


Extension Activities

Listed below are some optional activities in no particular order, to further your students’ learning.

Activity 1: Mathematics through encryption and RSA

Encryption can create a sense of intrigue for students and can give context and practical applications for often abstract subjects in maths.

Through using and cracking cyphers such as substitution and Vigenère cyphers, students can discover the usefulness of statistics.

You can use this website http://www.xarg.org/tools/caesar-cypher/ to quickly encode a piece of text. You can then run basic frequency analysis of the cypher text letters to crack the cypher.

You can also crack substitution encryptions of other languages quite easily using frequency analysis. Give students a page or book of Spanish so that they can create a frequency fingerprint of that language then use that to crack the Spanish encryption.

Possible activity for performing frequency analysis could be to get students to write Java/Python script to perform the function on a substitution cypher.

The RSA method of encryption incorporates higher levels of maths and could be used in class’ 7-12 to teach various topics listed below depending on how deep you want to go.

It covers exponentials, integer arithmetic, prime numbers, co-prime numbers and modular/clock arithmetic.

 

Activity 2: Explore other cyphers

There are many creative cyphers that have been created throughout history. Some are really fun to create, use and research, scytale, rail fence are great ones but there are a lot more which can be found here https://en.wikipedia.org/wiki/Category:Classical_cyphers

 

Activity 3: Computer science

Encryption is an important part of computer science and computer security. There are a lot of other cool topics in computer science. Counting in binary, hexadecimal, barcodes, what is the internet?

A good resource for teaching computer science is https://picoctf.com/. This website was set up in 2014 and 2013 as a computer security competition for high school students, although the competition is no longer running, the game is still free to use. Students work in teams to try to solve, hack and decrypt their way to a solution. The problems vary in difficulty but are designed to work for students in the 6th to 12th grade and even above. Some problems are designed to be solved quite easily and some are designed to be really difficult. As they go through the challenge student they learn skills regarding cryptography and computer science.

 

Activity 4: Steganography

Steganography is related to encryption, however instead of scrambling a message it is the art of hiding message in plain sight. You can explore the various types of steganography in the classroom and how it is used today. Hollywood uses it to hide messages in its pre-release movies so that if their movie gets leaked they know who it came from. On the Questacon website we have hidden a virtual Easter egg. There is a picture with a secret message embedded within it using steganography. First students will need to locate the right picture, then use the following website to decode what the secret message is https://futureboy.us/stegano/decinput.html. The hidden message has been encrypted, so to find it students will first need to decrypt it using the methods we have shown then in the Virtual Excursion. If they want to perform a frequency analysis on the cypher text to decode it they can use the tool on Kahn academy found here https://www.khanacademy.org/computing/computer-science/cryptography/crypt/p/frequency-fingerprint-exploration  you just need to type the cypher text in.

Curriculum links

 

Australian National Curriculum Online: http://www.australiancurriculum.edu.au/ - 4/5/2016

Digital Technologies

 

Digital Technologies Knowledge and Understanding

Digital Technologies Processes and Production Skills

Year 5 & 6

Examine how whole numbers are used to represent all data in digital systems  (ACTDIK015)

Design, modify and follow simple algorithms involving sequences of steps, branching, and iteration (repetition)  (ACTDIP019)*

Year 7 & 8

Investigate how digital systems represent text, image and audio data in binary (ACTDIK024)

Design algorithms represented diagrammatically and in English, and trace algorithms to predict output for a given input and to identify errors (ACTDIP029)*

Year 9 & 10

Investigate the role of hardware and software in managing, controlling and securing the movement of and access to data in networked digital systems (ACTDIK034)

Design algorithms represented diagrammatically and in structured English and validate algorithms and programs through tracing and test cases (ACTDIP040)*

*Although not covered in this Virtual Excursion explicitly, cyphers are generally just an algorithm, a set of rules that need to be operated on a certain text in a certain order. In this way encryption can be used as an interesting tool for teaching students to design and evaluate algorithms covering various points in the curriculum such as (ACTDIP040) (ACTDIP029) (ACTDIP019)

Mathematics

 

Number and Algebra

Statistics and probability

Year 6

 

Interpret and compare a range of data displays, including side-by-side column graphs for two categorical variables (ACMSP147)

Year 7

 

Construct and compare a range of data displays including stem-and-leaf plots and dot plots(ACMSP170)

Year 8

 

 

Year 9

 

Construct back-to-back stem-and-leaf plots and histograms and describe data, using terms including ‘skewed’, ‘symmetric’ and ‘bi modal’(ACMSP282)

comparing means, medians and ranges of two sets of numerical data which have been displayed using histograms, dot plots, or stem and leaf plots (ACMSP283)

Although the Virtual Excursion doesn’t cover Number and Algebra, some of the encryption methods, particularly the RSA method of encryption, could be used in the classroom to give context to various number concepts, see extension activity 2 for possible topics covered. Potential links Year 7 (ACMNA149), Year 9 (ACMNA122).

Science

This Virtual Excursion does not cover the science understanding or inquiry streams of the curriculum, however it does follows the story of how encryption has changed over time, from Julius Caesar to the modern age. We look at how new technologies have driven the need to come up with new ways of encrypting information and decrypting information. Many of these new technologies are linked to scientific discoveries, eg. invention of the computer, increase in processing power, new capabilities in computing, quantum computing. In this way it could fit within Science as a Human Endeavor stream (ACSHE119)

(ACSHE120) (ACSHE135)(ACSHE135) (ACSHE158) (ACSHE192)

 

Appendix

Vigenere Cypher Table

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