A PEM file, or Privacy Enhanced Mail, is a file format for storing and sharing cryptographic certificates and keys that play a crucial role in SSL/TLS certificates to secure web connections. While these files were initially used for secure email transfers, they now serve as certificate files that enable encrypted communication across platforms and improve cybersecurity.

This article walks you through what a .pem file is in detail, how to create it, and how to open it.

What Is a PEM File

A PEM file, or Privacy Enhanced Mail, is a file format that contains cryptographic data, such as private keys, SSL/TLS certificates, and trusted certificate authorities. It allows storage of multiple certificate blocks in a single file and is generally used when applications need a whole certificate chain for installation. This Base64-encoded file is used in SSL/TLS configurations, SSH protocols, and servers for secure communications. Saved in ASCII format and easily read/edited with a text editor, PEM files have extensions such as .pem, .cer, .crt, and .key.

How to Create a PEM File

You can create a PEM file using OpenSSL. OpenSSL is an open-source toolkit for generating and working with PEM files. Below is how to use it.

• Generate the private key openssl genrsa -out private.key 2048 and save it to private.key. For higher-security environments, use 4096-bit.
• Generate a self-signed certificate openssl req -new -x509 -key private.key -out certificate.crt -days 365. OpenSSL prompts you for your country, domain (Common Name), and organization name. The -days 365 specifies the certificate’s validity period.
• Convert private key to PEM openssl rsa -in private.key -out private.pem.
• Convert certificate to PEM openssl x509 -in certificate.crt -out certificate.pem.

After creating a PEM file, you can open and view it easily.

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How to Open and View a PEM File

To open and view a PEM file, you can use a text editor or the OpenSSL command line. Below are both methods explained.

Opening and viewing a PEM file using a text editor

Since a PEM file is text-based, you can open it in any of the best text editors, such as Notepad on Windows or TextEdit on Mac. Once you open the PEM file in the desired text editor, the file appears in Base64 encoding.

Using the OpenSSL command line

OpenSSL is a tool for easy PEM file management and viewing. OpenSSL commands provide complete information about the keys, certificates, and other details in PEM files. Use the OpenSSL command openssl x509 -in filename.pem -text -noout to get PEM file contents in the terminal.

However, if you experience any issues with the PEM files, you can check the guide below for solutions.

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Common PEM File Errors and Solutions

Below are some common issues with PEM files and how to fix them.

• PEM file is rejected during installation: The PEM file may be rejected during installation due to an incorrect certificate order. To fix this issue, use the correct order for the target scenario to rebuild the PEM file.
• Trust chain errors: Trust chain errors occur because of an incorrect intermediate or root certificate. To fix this, download the correct root and intermediate certificates.
• SSL/TLS service fails to start: The SSL or TLS service may fail to start because the target application may need the private key in the PEM file. To troubleshoot this problem, create a PEM file with the private key and certificate chain if needed by the application.
• Invalid PEM file format: Invalid PEM file format may be a result of missing BEGIN or END tags. To fix this issue, verify that every key and certificate block has the necessary BEGIN and END lines.
• Trust warnings: If installation succeeds but trust warnings persist, the PEM file may have an incomplete or incorrect chain. To solve this problem, check the chain requirements for the target app and rebuild the PEM file with the correct certificate.
• Unable to load certificate: The certificate may be corrupted or invalid. To fix this, re-export the certificate from its source or request a new certificate.

Below are a few common questions answered about PEM files to clear up persistent doubts.

Frequently Asked Questions

Q1. How to generate a PEM file?

You can generate a PEM file with OpenSSL, a popular tool for creating and working with PEM files.

Q2. Is a PEM file the same as a CER file?

No, a PEM file and a CER file are not the same. PEM is a text-based format for SSL certificates; it is Base64 encoded, and you can open it in any text editor. CER files only contain the SSL certificate without a private key.

Q3. Is a PEM file the same as a CRT?

CRT, like CER files, contains only the SSL certificate and not a private key; PEM contains both the SSL certificate and a private key.

Hopefully, this clears up all your doubts about PEM files. If you have any pending questions or concerns, leave us a comment.