This week we looked at classical ciphers. I enjoyed this, looking at the ingenious ways that clever people have come up with hiding messages in the past. It’s also appealing because although these techniques might be outdated and easily broken with a computer, they are a fun and understandable introduction to hiding information.
I chose the rail-fence cipher. I like the simplicity of it and the ability to encode and decode a message quickly. I wouldn’t use it for nuclear launch codes, but I would for the time and location of a secret party
Some other classic ciphers include:
- Caesar cipher
- Monoalphabetic Substitution Cipher
- Vigenère Cipher
- Polybius Cipher
- Playfair Cipher
- Atbash
- Rail Fence
- Scytale
- Permutation
The key for the rail fence is the number of rails on the fence. Once this is set, you simply write your message zigzagging across the fence.
Example
Quick dirty secret => QUICKDIRTYSECRET
Key: 4
Creating the cipher, we simply start on the left on the ‘top rail’ and write the first letter, then move down one rail and across a corresponding distance to the right. When you get to the bottom rail, simply move up and to the right.
A picture is worth a thousand words
Reflection
This is so simple and ingenious with the zigzag on the paper acting like a mechanical device to perform the transposition. I’m attracted to the ‘mechanical’ aspect of it. Perhaps because it is intuitive but I think because of my penchant for disaster movies, I have the end of civilisation in the back of my head – codes like this would work well in a scenario like this. I’ve always thought of codes in terms of an algo, but using something as simple as a piece of paper and a shared template could create something quite mathematically difficult to deduce.
A useful link for de/enciphering is: https://www.dcode.fr
