# SSL Certificate Private Key Validation

> Validating SSL Certificate and Private Key with a simple Python script

- Canonical URL: <https://carlossura.com/blog/ssl-certificate-private-key-validation/>
- Author: Carlos Sura
- Published: 2026-05-26
- Tags: ssl, certificate, key, python

I had an issue the other day with an SSL Certificate and Private Key that didn't match. Here is how I validated it.

First, ensure you have the `cryptography` library installed.

```
pip install cryptography
```

Then, use the following script to validate the SSL Certificate and Private Key.

```
from cryptography.hazmat.primitives.asymmetric import rsa
from cryptography.hazmat.primitives import serialization
from cryptography.x509 import load_pem_x509_certificate

# Load private key
with open("your-private.key", "rb") as key_file:
    private_key = serialization.load_pem_private_key(key_file.read(), password=None)

# Load certificate
with open("your-certificate.pem", "rb") as cert_file:
    cert = load_pem_x509_certificate(cert_file.read())

# Get the public key from the certificate
public_key = cert.public_key()

# Check if the public key matches the private key
if isinstance(public_key, rsa.RSAPublicKey) and isinstance(private_key, rsa.RSAPrivateKey):
    if private_key.public_key().public_numbers() == public_key.public_numbers():
        print("The private key belongs to the certificate.")
    else:
        print("The private key does NOT belong to the certificate.")

```

I ran this script, and it told me that the private key did not belong to the certificate. So I knew I had the wrong private key. This saved me a lot of time troubleshooting.