About

bletchley is a pure Python cryptographic tool suite. It provides historical ciphers. In the future it will also provide cryptographic attacks (cryptanalysis) to use against these ciphers.

If you find an bug or have a feature you'd like to see, please raise an issue.

You can get in touch with us via this link.

The latest version of Bletchley is available via our GitLab repo, PyPi or Conda-forge.

Ciphers

Supported ciphers can be found on our wiki.

Simple Example

Ciphers can be accessed by adding bletchley to your Python path:

export PYTHONPATH=$PYTHONPATH:/path/to/bletchley

Then importing bletchley into your Python script:

from bletchley.ciphers.rot13_cipher import ROT13Cipher

And creating an instance of the cipher:

my_cipher = ROT13Cipher()

From here, you can encrypt and decrypt messages using the cipher:

my_message = "Hello World!"
cipher_text = my_cipher.encrypt(my_message)
plain_text = my_cipher.decrypt(cipher_text)

Advanced Example

All ciphers implement the abstract class: Cipher. This means that all ciphers have encrypt and decrypt functions you can use. Note that some more complex ciphers (such as the VIC Cipher) may have additional arguments when called. Where possible, these will be included with the cipher.

Taking the VIC cipher as an example, another argument is needed to encrypt/decrypt messages. This is called a 'checkerboard'. We can create our cipher in the same way as we did for the Caeser cipher before:

from bletchley.ciphers.vic_cipher import VICCipher
my_cipher = VICCipher()

Before we can encrypt/decrypt any message, a checkerboard is needed. We now have two options:

1. Create our own checkerboard
2. Let the VIC cipher generate a random checkerboard for us

For now we will choose the easier of the two, and let the VIC cipher generate a checkerboard for us:

my_checkerboard = my_cipher.generate_checkerboard()
my_message = "Hello World!"
cipher_text = my_cipher.encrypt(my_message, my_checkerboard)
plain_text = my_cipher.decrypt(cipher_text, my_checkerboard)

The checkerboard, in this example, could be exported and saved for future use.

Cryptanalysis

Supported cryptanalysis tools can be found on our wiki.

Contributing

To help Bletchley's continued development, please consider contributing to the project (you can find our contribution guide here).