Cryptography Lesson 1 - Teacher's Plan

Short Summary

Guides

Further material and introduction to cryptography, encryption, decryption, ciphers and the key exchange problem:

The Key Exchange Problem https://www.youtube.com/watch?v=U62S8SchxX4

Alice and Bob and all https://en.wikipedia.org/wiki/Alice_and_Bob

Visual Cryptography https://www.cl.cam.ac.uk/~fms27/vck/vck-poster.pdf

Public Key Cryptography - Computerphile https://www.youtube.com/watch?v=GSIDS_lvRv4

Public Key Encryption http://csunplugged.org/public-key-encryption/#Related_Resources

Journey into Cryptography - Khan Academy https://www.khanacademy.org/computing/computer-science/cryptography#random-algorithms-probability

ROT13 - Wikipedia https://en.wikipedia.org/wiki/ROT13

Xor - Wikipedia https://en.wikipedia.org/wiki/Exclusive_or

GCHQ - Cryptoy https://www.gchq.gov.uk/features/cryptoy-explore-fascinating-world-cryptography

Frank Tapson - Public Key Cryptography http://www.cimt.org.uk/resources/topics/art003.pdf

Updated: June 2017

Learning Objectives

  1. To introduce, in a practical way, the protocols of symmetric and asymmetric cryptographic systems;
  2. To define, in a number of senses, what a key is, and how they can be exchanged - in secret;
  3. To use and understand a simple substitution (or shift) cipher (Caesar’s Cipher);
  4. To experience a more complex piece of visual cryptography and consider how it was made;
  5. To introduce an overview for how easy encryption techniques are made hard, with mathematics.

Cross-curricular applications

Mathematics: randomness, factors, prime numbers, modular arithmetic.

Lesson Summary

A practical demonstration of the key exchange problem.

Starter

Briefly discuss the main terms and some of the reasons we need secure, private electronic communication channels.

Main development

Demonstrate the key exchange solution in practice.

Plenary

Discuss keys: understand the nature of public and private keys.

Discuss weak encryption: introduce frequency analysis

Work in some ‘analogies’ of how more complex systems of encryption might work. Enigma

Extension

Consider the mathematical principles in some of the common cryptographic algorithms: