[Tut] Two Easy Ways to Encrypt and Decrypt Python Strings

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Two Easy Ways to Encrypt and Decrypt Python Strings

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Today I gave a service consultant access to one of my AWS servers. I have a few files on the server that I was reluctant to share with the service consultant because these files contain sensitive personal data. Python is my default way to solve these types of problems. Naturally, I wondered how to encrypt this data using Python — and decrypt it again after the consultant is done? In this article, I’ll share my learnings!

Question: Given a Python string. How to encrypt the Python string using a password or otherwise and decrypt the encrypted phrase to obtain the initial cleartext again?

There are several ways to encrypt and decrypt Python strings. I decided to share only the top two ways (my personal preference is Method 1):

Method 1: Cryptography Library Fernet



To encrypt and decrypt a Python string, install and import the

Code:

cryptography

library, generate a Fernet key, and create a

Code:

Fernet

object with it. You can then encrypt the string using the

Code:

Fernet.encrypt()

method and decrypt the encrypted string using the

Code:

Fernet.decrypt()

method.

If you haven’t already, you must first install the

Code:

cryptography

library using the

Code:

pip install cryptography

shell command or variants thereof. See more here.

Here’s a minimal example where I’ve highlighted the encryption and decryption calls:

Code:

# Import the cryptography library from cryptography.fernet import Fernet # Generate a Fernet key key = Fernet.generate_key() # Create a Fernet object with that key f = Fernet(key) # Input string to be encrypted input_string = "Hello World!" # Encrypt the string encrypted_string = f.encrypt(input_string.encode()) # Decrypt the encrypted string decrypted_string = f.decrypt(encrypted_string) # Print the original and decrypted strings print("Original String:", input_string) print("Decrypted String:", decrypted_string.decode())

This small script first imports the

Code:

Fernet

class from the

Code:

cryptography

library that provides high-level cryptographic primitives and algorithms such as

• symmetric encryption,
  
  
• public-key encryption,
  
  
• hashing, and
  
  
• digital signatures.
  

A Fernet key is then generated and used to create a

Code:

Fernet

object. The input string to be encrypted is then provided as an argument to the

Code:

encrypt()

method of the

Code:

Fernet

object. This method encrypts the string using the Fernet key and returns an encrypted string.

The encrypted string is then provided as an argument to the

Code:

decrypt()

method of the

Code:

Fernet

object. This method decrypts the encrypted string using the Fernet key and returns a decrypted string.

Finally, the original string and the decrypted string are printed to the console.

The output is as follows:

Code:

Original String: Hello World! Decrypted String: Hello World!

Try it yourself in our Jupyter Notebook:



Method 2: PyCrypto Cipher



Install and import the PyCrypto library to encrypt and decrypt a string. As preparation, you need to make sure to pad the input string to 32 characters using

Code:

string.rjust(32)

to make sure it is the correct length. Then, define a secret key, i.e., a “password”. Finally, encrypt the string using the AES algorithm, which is a type of symmetric-key encryption.

You can then decrypt the encrypted string again by using the same key.

Here’s a small example:

Code:

# Import the PyCrypto library import Crypto # Input string to be encrypted (padding to adjust length) input_string = "Hello World!".rjust(32) # Secret key (pw) key = b'1234567890123456' # Encrypt the string cipher = Crypto.Cipher.AES.new(key) encrypted_string = cipher.encrypt(input_string.encode()) # Decrypt the encrypted string decrypted_string = cipher.decrypt(encrypted_string) # Print the original and decrypted strings print("Original String:", input_string) print("Decrypted String:", decrypted_string.decode())

This code imports the PyCrypto library and uses it to encrypt and decrypt a string.

The input string is

Code:

"Hello World!"

, which is padded to 32 characters to make sure it is the correct length.

Then, a secret key (password) is defined.

The string is encrypted using the AES algorithm, which is a type of symmetric-key encryption.

The encrypted string is then decrypted using the same key and the original and decrypted strings are printed. Here’s the output:

Code:

Original String: Hello World! Decrypted String: Hello World!

Try it yourself in our Jupyter Notebook:



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