#ciphers and codes

[tea-and-procrastination]

Dr Hannah Fry: Codebreaker - BBC Sounds

Dr Hannah Fry brings you the best in codes, ciphers and secrets from the BBC Radio archive

Bletchley Circle fans, you may find this interesting! Three whole hours of archive programmes on code-breaking. I’ve only listened to the first part so far, but according to the description there’s a segment on the girls who worked at Bletchley.

[ciphers-and-tea]

The Difference Between Codes and Ciphers

Sometimes when writing, the topic of a secret message crops up. Often times, the solution on how to write that secret message is to have it be in Code. However, the word Code in this situation is used to talk about Codes and Ciphers, which are two different methods.

Codes are Words, Numbers, Letters or Symbols used to represent Words or Phrases. 

Ciphers are Numbers, Letters or Symbols used to replace the Alphabet used when writing your message

It’s easy to create a code, but the more complex the message and the code, the more likely a code book would be needed and they would end up carrying a large code book just in order to write a letter

However, with a cipher, once part of it is broken, it is possible to use that to figure out the rest of the message. Whereas if one word in a code is figured out, the rest of the code is independent enough that it would be more difficult to use that to crack the rest of it.

[ciphers-and-tea]

Making a Cipher for my WIP

I’m currently planning and developing my WIP project, a modern urban fantasy retelling of Rapunzel with less princes and more thieves. One thing that I’m planning to include is Rapunzel, whose name is Ari, and one of the thieves exchanging encrypted messages.

Which means I need to make a cipher.

I don’t actually need to make a cipher. But I want to.

There are different steps to creating a cipher, questions you want to answer. This ties into who’s creating the cipher and why? As well as how important the message that being encrypted is.

For me, the things to keep in mind are

Ari is the one to initiate

Nothing Top Secret is being shared, but she doesn’t want anyone to know what she’s doing

The first message will be deciphered 

The cipher will become more complex with each message sent between the two

So I’m probably going to end up making multiple ciphers that increase in complexity

Let’s start with the cipher that will be the base for the rest of them: the cipher that will be in the first letter. First things first is to write out the plain alphabet since my plan is start with a simple keyword cipher

Then we figure out what the keyword is going to be.

I’m going to have the keyword be the name that Ari will sign the letter with. That way the keyword will be included in the letter. This does mean that the cipher will be easier to crack, but since it’s not meant to hide secret information and instead open a line of communication, I’m okay with that. Do remember to keep in mind that you don’t repeat letters in a keyword.

Then we fill in the rest of the alphabet. Remember that we don’t repeat  letters we’ve already used in the keyword.

Now we have a completed keyword cipher, ready for use.

[ciphers-and-tea]

Cryptography - Letter Frequency

Letter Frequency is extremely important when it comes to deciphering a message. It isn’t a perfect solution that instantly deciphers, but the letter frequency of the language the plain text of the message was written in can help identify parts of the cipher.

This is a system that is more effective with a longer message, since it relies on finding the letter or symbols that show up the most frequently. These frequent letters or symbols are most likely going to reflect the most frequent letters in the original language.

One thing to be aware of is that if a language has a major spelling change, there is a chance that letter frequency may change. This happened with Russian after a spelling change came about after the Bolsheviks in the early 1900s.

So if a character is planning on deciphering an intercepted message, chances are, they’ve got a chart that provides the letter frequency for their language.

[ciphers-and-tea]

More Cipher Development

For my WIP I’m creating a cipher. 

Or to be more exact, ciphers. 

The cipher used by two of my main characters is a cipher that will grow and develop throughout the story. This allows for the two using the cipher to bond over something they’ve both created. And it allows me to a huge dork.

This is the third development for the cipher.

For this cipher, instead of growing from the end result of the previous cipher, we’re actually going to go back just a little. And we’re going to utilize the fun little cube that we made.

From there, we’re going to change this cipher in a way that will look radically different in a written letter, but involves only a few short steps.

First Things First: put it in a box

This is purely for organization, but it helps keep things from getting muddled in the next step

Then we number the rows and columns. What this does is allows us to shift from a code that still uses letters, to one that uses numbers.

To use this cipher, you locate the letter you want to use. Let’s say I wanted to write the word “fuck”. “F” could be written as either “24″ or “42″. I could make the decision to put the numbers in row-column order, column-row order, or willy nilly. “U” could be “13″ or “31″. And so on. “C” would be “22″. “K” would be “34″ or “43″.

So ultimately, I could write the word “Fuck” in a multitude of ways depending on which order each number set was in.

And if you were deciphering this, each number could be two different letters. “42 13 22 34″ could be “fuck”, but it could also be “ohcp”.