How to Convert a Certificate (CER) to a PFX Using OpenSSL

Learn how to convert a certificate file in CER format to a PFX file using OpenSSL, a widely-used tool for managing SSL/TLS certificates and keys. This step-by-step guide will show you the commands needed to perform the conversion.
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If you have a certificate file in CER (or DER) format and need to convert it to a PFX file (also known as PKCS12 format) for use with servers or applications that require both the certificate and its private key in a single file, OpenSSL can be a helpful tool. Here's how you can do it step by step:

Step 1: Prepare Your Files
Ensure you have the following files ready:

Certificate file in CER format: This is your public certificate file.

Private key file: You must have the corresponding private key file. If you don't have the private key, you won't be able to create the PFX file.

Step 2: Convert the Certificate and Key to PEM Format
OpenSSL typically works with PEM-encoded files, so if your certificate and key are not already in PEM format, convert them first.

Convert the CER certificate file to PEM format:

[[See Video to Reveal this Text or Code Snippet]]

Convert the private key to PEM format if it's not already in PEM format:

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Step 3: Combine Certificate and Key into a PFX File
Now that you have both the certificate and the private key in PEM format, you can combine them into a PFX file.

Use the following OpenSSL command to create the PFX file:

[[See Video to Reveal this Text or Code Snippet]]

You will be prompted to enter a password for the PFX file. This password will be needed when using the PFX file in applications that require it.

Step 4: Verify the PFX File
Once the conversion process is complete, you can verify the contents of the PFX file using OpenSSL:

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You'll be prompted to enter the password you set during the PFX creation process. This command will display information about the contents of the PFX file, including the certificate and private key.

That's it! You've successfully converted a certificate from CER format to PFX format using OpenSSL. Now you can use the PFX file in applications or servers that require this combined format.