Cryptography getting started


Martin McBride, 2020-02-22
Tags installing anaconda
Categories cryptography

This article is part of a series on the Python cryptography library.

The cryptography module can be installed using pip, like this:

pip install cryptography

If you use Anaconda, you can also install cryptography in the usual way with conda.

Building the module yourself

Both pip and conda download a pre-built executable from a repository. There is, at least theoretically, a possibility of an attacker hacking the repository and replacing the original executable with their own doctored version, that might contain back doors.

If your application requires a high degree of security, you should consider building the library yourself. Instructions for doing this are included on the official cryptography module website at cryptography.io.

Checking the module

You can check that the module is installed correctly using this simple program that creates a key then encodes and decodes a message:

from cryptography.fernet import Fernet

# Generate a key
key = Fernet.generate_key()

# Create a Fernet instance with the key
cipher = Fernet(key)

# Encrypt a message
message = "Message to be encrypted".encode('utf-8')
token = cipher.encrypt(message)
print(token.hex())

# Decrypt the cipertext
decoded = cipher.decrypt(token)
print(decoded)

The line print(token.hex()) should print the encrypted message, something like:

674141414141426555704e5a6e423947
333562524c504b333751745a47576432
3266305a6a33356c3645304838425446
316e5a58627850634741425f30545576
6b637956526e30664d75523337325261
776a543375785a677a64434353527142
61516e7446766f326f6d4a6c4d313363
84449776f4a673d

The encrypted data will be different every time, because it contains random elements.

The line print(decoded) prints the result of decrypting the token. It should be:

b'Message to be encrypted'

We will look at this code in more detail in the Fernet encryption section.

If you found this article useful, you might be interested in the book Functional Programming in Python or other books by the same author.

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