Behind-The-Scenes Guide To Cryptography

Interested in the inner working of cryptographic tools? Mike Bedford provides a hands-on introduction to the technology of cryptography.

Cryptography – rendering a message or data unintelligible to any unauthorised party – is commonly used to protect data on a hard disk in the case of loss or theft, or to obfuscate data that’s transmitted online.

It’s a vital tool in everyday activities such as online banking, where it works behind the scenes, and you may well use encryption tools on your PC. Here we put cryptography under the spotlight. However, this isn’t a guide on how to use cryptographic tools for real-world applications. Instead, because the underlying technology is a mystery to many, we aim to help you to understand the principles and see how today’s ciphers came about.

To guide you in this voyage of discovery, we’ll use some excellent open source software that will give you hands-on experience, and we’ll also suggest some exercises that you could undertake by hacking your own code. Our software of choice, JCrypTool, is a valuable educational resource, and we’ll illustrate some of the ciphers we discuss by reference to this software. However, that’s only scratching the surface of its capabilities so, if you want to learn more about this fascinating subject, we suggest you delve further into JCrypTool yourself.

Note that this article is intended to inform you, not to provide practical guidance on real-world cryptography. So, while we encourage you to try out ideas with your own code, we don’t recommend that you use your code to protect your most valuable secrets. Mistakes won’t always be obvious and the risk of getting it wrong is just too great. Furthermore, if you have a real need for encryption, we recommend that you read several impartial reviews before making your choice. And finally, before getting bogged down in unfamiliar terminology, we suggest you get up to date on the language of cryptography by looking at the box just over there…