Step by Step Procedure to Convert a CER Certificate to PFX Without the Private Key

Before jumping into the procedure to convert a CER certificate to PFX without the private key. Let’s understand the difference between the certificate formats.

You can always refer X.509 certificate Request for Comments (RFC) and X.509 articles to know about the digital certificates in depth. X.509 certificates come majorly in two formats: 

Again there are two formats underneath Base64. They are PEM and PKCS#7. As like Base64, Binary has two formats too: DER and PKCS#12.

Of all these certificate formats few of them come bundled with a private key and few are not. To tell in short, .cer, .crt, and .p7b formats necessarily don’t have the private key with them. Whereas .pfx is always bundled with a private key.

Most of the Certificate Authorities will not issue certificates with the private key. They just issue and share the certificates in .cer, .crt, and .p7b formats which don’t have the private key in most of the cases. But, your application needs the certificate in .pfx format. Now, you have a .cer certificate in your hand, but you need a .pfx certificate to deploy. And, you can’t convert the .cer certificate to .pfx without the private key. This problem has created confusion in most people and may create delays in the certificate deployment/renewal process.

We thought it is an excellent idea to address this common problem. So we are here to explain the complete step by step process to convert a CER Certificate to PFX Without the private key.

Overview of CER and PFX Certificates

Since, we are dealing with two commonly used certificate formats: CER and PFX. Let’s learn more about them. Both CER and PFX are for different purpose.

You might know that digital certificates are used for two main reasons:

CER or CRT files contain the public key and other certificate information in a binary DER encoded format or Base64 encoded PEM format. Since it only has the public key, it is most likely used to complete three-way handshake. On the other hand, since it doesn’t bundled with private key, It cannot be used alone for authentication.

PFX or PKCS #12 files contain the public key, private key, and certificate chain in an encrypted container. The private key allows PFX files to be used for authentication purposes.

PFX files are more versatile as they bundle both public and private keys. CER files are easier to distribute publicly since they only contain the public key.

Common uses of CER files include distributing public keys and root/intermediate certificates. PFX files are used for authentication in applications and web servers.

CER vs PFX

When to Convert CER to PFX?

You may need to convert a CER file to PFX format in situations like:

In these cases, just the public CER certificate won’t work since the private key is also needed. Converting it to PFX format bundles the cert and private key.

How to Convert a CER Certificate to PFX Without the Private Key (On Windows)?

The procedure is quite simple. You can convert a CER certificate to PFX without the private key in three simple steps. But, this process will require the machine on which you have created the CSR (Certificate Signing Request) Because the private key had been created during the CRS creation process. We are just using the previously create private key to convert the CER certificate to PFX. Bear in mind, this process will work only on Windows platform.

This process has been divided into three simple tasks:

Step 1: Import the certificate to its personal certificate store

Right-click on the certificate file.
Select install certificate.

Step 2: Select the Local Computer radio button

Step 3: Select the default automatic store to import the certificate

Step 4: Import the certificate

Click the Finish button to complete the import process.

Step 5: Import process complete.

Wait for a while until you see a successful message.