Tutorial on digital cryptography

Harold Thimbleby


Digital cryptography raises many new ethical issues, but is poorly understood. Unfortunately, modern cryptography is often explained using complicated mathematics, but this sophistication is unnecessary to understand the principles.

This tutorial explains the principles of digital cryptography using clear participative exercises. Attendees will gain an insight into the powers and methods of digital cryptography, and public key cryptography in particular. Attendees will be able to send secure public key encrypted messages (e.g., across the lecture theatre) using pencil-and-paper techniques. The tutorial will also show how new ideas, apparently nothing to do with cryptography, can be supported: such as digital cash and solutions to mind bogglers like:

  • I want to make a fair choice with someone I am telephoning, something that might ordinarily be done by tossing a coin. However, how can I trust the other person to toss the coin fairly, or how can they trust me?

Hence the technical relation of cryptography to trust will become much clearer.

The approach has been used with many audiences, from school children to post graduate specialists. All have appreciated the new insights gained.