Cryptography implementations

The ciphers/ directory contains implementations of various cryptographic ciphers.

Requirements

• Python 3.x

Currently available ciphers

Shift Cipher

The shift_cipher.py script implements a shift cipher, also known as a Caesar cipher. It encrypts and decrypts text by shifting each letter a fixed number of positions down the alphabet.

Usage

The script is run from the command line and takes the following arguments:

• --text: The text to be encrypted or decrypted. (Required)
• --key: The integer key used for the shift. A positive key shifts letters forward; a negative key shifts them backward. (Required)
• --decrypt: A flag that, when present, tells the script to decrypt instead of encrypt. (Optional)

Examples

1. Encrypting text:

To encrypt the text "hello" with a key of 3:

python shift_cipher.py --text "Hello world!" --key 3
# returns "khoorzruog"

2. Decrypting text:

To decrypt the text khoorzruog:

python shift_cipher.py --text "khoorzruog" --key 3 --decrypt
# returns "helloworld"

or you could alternatively run:

python shift_cipher.py --text "khoorzruog" --key -3
# also returns "helloworld" 

Contributing

Contributions are welcome! If you'd like to add more ciphers or improve existing implementations, please feel free to open a pull request.