How to Extract Public Keys from Base64 Encoded Strings in Python

Learn how to extract public keys from base64 encoded strings in Python using the `cryptography` library, with an easy-to-follow solution based on x509 certificates.
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Extracting Public Keys from Base64 Encoded Strings in Python

In the world of cryptography, handling certificates is a common task, particularly when you're working with secure communications and data encryption. You may find yourself needing to extract a public key from a base64 encoded certificate string, especially if you're transitioning from a Java application where this is straightforward.

This guide will guide you through the process of extracting a public key from a base64 encoded string in Python, using the cryptography library.

The Problem: Extracting a Public Key

Imagine you have a certificate that’s presented to you in a base64 encoded format. For instance, in Java, you can easily extract the public key by decoding the base64 string and using the X509Certificate class. Here’s how it looks:

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Now, if you’re looking to do the same thing using Python, you may be wondering how to achieve this. Let’s break it down.

The Solution: Using the cryptography Library

Python provides an excellent package called cryptography, which allows you to work with certificates and keys easily. Follow these steps to extract the public key from your base64 encoded string.

Step-by-Step Process

Install the cryptography Library:
If you haven't installed it yet, you can do so using pip:

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Prepare the Certificate String:
Ensure your base64 encoded certificate string is surrounded by the required header and footer:

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Load the Certificate and Extract the Public Key:
Here is how the Python code will look:

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Understanding the Code:

load_pem_x509_certificate: This function takes a byte string of the encoded certificate and returns a certificate object.

str.encode: This method converts your string to bytes, which is needed by the load_pem_x509_certificate method.

public_key(): This method retrieves the public key associated with your certificate.

Conclusion

Now you have successfully extracted a public key from a base64 encoded certificate string in Python! This key can now be used for various cryptographic operations, such as encrypting JWT tokens for secure communication.

Feel free to reach out if you have any questions or need further assistance with cryptography in Python!