Understanding the Certificates

Before diving into the process of converting a cer file to pem OpenSSL, it is essential to understand what certificates are and their significance. A certificate is an electronic document that is used to verify the identity of a website or an individual. It is a way of ensuring that the information provided by a website is valid and secure. Certificates are issued by trusted third-party organizations, known as Certificate Authorities (CAs).

Different Types of Certificates

There are different types of certificates, such as SSL, TLS, and X.509. SSL (Secure Sockets Layer) and TLS (Transport Layer Security) are encryption protocols that are used to secure the communication between two devices. X.509 is a standard for public key infrastructure that defines the format of certificates. Each certificate has a unique identifier, known as a fingerprint, which is used to validate the certificate.

Cer File and Pem OpenSSL

A cer file is a binary format of a certificate that is used in the Windows operating system. On the other hand, pem OpenSSL is a text-based format of a certificate that is used in Unix-based operating systems. The process of converting a cer file to pem OpenSSL is essential when you want to use a certificate in a Unix-based system.

Converting Cer File to Pem OpenSSL

Step 1: Downloading OpenSSL

The first step in converting a cer file to pem OpenSSL is to download and install OpenSSL on your system. OpenSSL is an open-source software library that provides cryptographic functions for various platforms, including Unix-based operating systems.

Step 2: Converting the Cer File to Pem Format

Once you have installed OpenSSL on your system, you can start the process of converting the cer file to pem format. To do this, you need to open the command prompt and navigate to the directory where the cer file is located. Once you are in the directory, you can use the following command to convert the cer file to pem format:


In this command, “certificate.cer” is the name of the cer file, and “certificate.pem” is the name of the pem file that will be created after the conversion process.

Step 3: Verifying the Pem File

After the conversion process is complete, you should verify the pem file to ensure that it is valid. To do this, you can use the following command:

This command will display the details of the certificate, such as the issuer, subject, and validity period. If the details are correct, then the pem file is valid.

FAQs – Convert cer file to pem openssl

What is a cer file?

A cer file stands for “Certificate” file format, it is a digital certificate that is used to authenticate the identity of a server, computer, or client. These certificates can be used in a variety of situations, including securing web browsers, emailing, messaging, and more. They contain information about the public key, the name of the certificate holder, and the digital signature of the certificate authority.

What is a pem file?

A PEM (Privacy Enhanced Mail) file is a Base64 encoded DER certificate with a header and footer, that is also used for storing private keys. The pem file contains all the information represented in the cer file but also includes private keys and extracted public keys if any.

Why do I need to convert a cer file to a pem openssl?

Sometimes, you may need to export a certificate from one software system to another, and they may not accept the same file format. In particular, OpenSSL tools require the PEM format. When you initially receive a certificate, the format is often CER, and therefore, you may need to convert the certificate to PEM format to use it with OpenSSL.

What is OpenSSL?

OpenSSL is an open-source implementation of the SSL and TLS protocols. It is used for secure communication over computer networks, for example, between Internet browsers and web servers. OpenSSL provides a powerful suite of tools that can be used to generate, manipulate, and verify digital certificates and signatures.

How can I convert a cer file to a pem file using OpenSSL?

Converting a cer file to a pem using OpenSSL is relatively straightforward. You can use the following OpenSSL commands:

openssl x509 -inform der -in certificate.cer -out certificate.pem

This command reads a certificate in the DER format and converts it to a PEM-encoded certificate.

Alternatively, you can use the following command:

openssl x509 -in certificate.cer -out certificate.pem -outform PEM

This command reads a certificate in the default format and converts it to a PEM-encoded certificate.

Can I convert multiple cer files to pem files at once?

Yes, you can convert multiple certificate files to PEM format using the following OpenSSL command:

for f in *.cer; do openssl x509 -in “$f” -out “${f%.cer}.pem” -outform PEM; done

This command loops over all the .cer files in the current directory and converts them to PEM format. The resulting files have the same name as the original .cer file, but with the .pem extension.