# Enigma Machine
I still sort of remember being a kid and discovering that you could make a map of letters and from that have a simple
encoding mechanism.

For example (in the table shown below), the letter A would be encoded as M, B as N, C as O, and so on.

| Letter | Encoding |
|--------|----------|
| A      | M        |
| B      | N        |
| C      | O        |
| ...    | ...      |
| Z      | L        |

This is a [substitution cipher](https://en.wikipedia.org/wiki/Substitution_cipher) and is pretty simplistic by modern standards, but as a kid I thought it was cool [AF](https://www.howtogeek.com/711826/what-does-af-mean/).

One evening I was watching a video on YouTube about the Enigma Machine. It piqued my interest and I decided to make
something in Python to recreate the functionality.

## History
> The Enigma machine is a cipher device developed and used in the early- to mid-20th century to protect commercial,
> diplomatic, and military communication. It was employed extensively by Nazi Germany during World War II, in all
> branches of the German military. The Enigma machine was considered so secure that it was used to encipher the most
> top-secret messages.
> 
> The Enigma has an electromechanical rotor mechanism that scrambles the 26 letters of the alphabet. In typical use, one
> person enters text on the Enigma's keyboard and another person writes down which of the 26 lights above the keyboard
> illuminated at each key press. If plaintext is entered, the illuminated letters are the ciphertext. Entering
> ciphertext transforms it back into readable plaintext. The rotor mechanism changes the electrical connections between
> the keys and the lights with each keypress.
> 
> -- [Wikipedia](https://en.wikipedia.org/wiki/Enigma_machine)

## Usage
`uv run main.py "[message]" e|d [int]`

Where:
- __"[message]"__ is the message to be encrypted/decrypted. Should be in quotes.
- __e|d__ is the direction of the message (encrypt or decrypt).
- __int__ is the number of iterations to be made.

### Seed Values
When encrypting a message, a file will be written to the current directory. This file contains the seed values used to 
generate the encryption/decryption keys.

The seed values are integers between 0 and 58. In the file, each seed value is on a new line.

The number of iterations should match the number of seed values used.

### Examples
#### Encode
Encode the message "You are here." with three iterations.

`uv run main.py "You are here." e 3`

The command above will create a file called "seed_values.txt" with the generated seed values.

#### Decode
Decode the message "NTb!QDbGDQDa" with three iterations.

`uv run main.py '.NTb!QDbGDQDa' d 3`

The command above expects a file called "seed_values.txt" with the seed values used to encode the message from the preceding example.

## TODO
- [ ] Add a param to tell the `encode` function to use an existing seed file.