OpenSSL Command Line Basics

OpenSSL is a command-line tool that is used to generate and manage SSL certificates and private keys. It is a powerful tool that can be used to perform various tasks related to SSL certificates, including certificate conversion. OpenSSL is available on almost all Linux distributions and is easy to use.

Installing OpenSSL

Before you can use OpenSSL, you need to install it on your system. If you’re using a Debian-based distribution like Ubuntu or Debian, you can install it using the following command:

sudo apt-get install openssl

If you’re using a Red Hat-based distribution like CentOS, you can install it using the following command:

sudo yum install openssl

Converting CER to PEM

A CER file is a certificate file that contains a public key. A PEM file is a container format that contains a private key or a certificate. Converting a CER file to a PEM file is a simple process that can be done using OpenSSL.

Converting CER to PEM Using OpenSSL

To convert a CER file to a PEM file using OpenSSL, you can use the following command:

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

In this command, replace certificate.cer with the name of your CER file, and certificate.pem with the name of the PEM file you want to create.

Verifying the PEM File

To verify that the PEM file has been created successfully, you can use the following command:

openssl x509 -in certificate.pem -text -noout

This command will display the details of the certificate contained in the PEM file.

OpenSSL Command-line Interface

The OpenSSL command-line interface provides a set of commands that can be used to perform various tasks related to SSL certificates. Some of the common commands that you can use include genrsa, req, x509, pkcs12, and s_client.

The genrsa command is used to generate RSA private keys, while the req command is used to generate certificate signing requests. The x509 command is used to manage SSL certificates, while the pkcs12 command is used to create PKCS#12 files. The s_client command is used to test SSL/TLS connections.

FAQs – convert cer to pem openssl command line

What is a .cer file?

A .cer (or .crt) file is a digital certificate file used to authenticate or establish the identity of a web server, computer, or organization. It contains information about the public key of the entity it represents. These files are commonly used for secure communication over HTTPS and can be used to verify the identity of the server or client.

What is a .pem file?

A .pem file is a container format that may include a private key, a public key, or both. It is a base64 encoded file that contains ASCII lines that describe the certificate, key, or chain. PEM files are widely used in open source encryption and authentication protocols and are typically used when requesting an SSL certificate from a certificate authority or when integrating a certificate into a server.

How do I convert a .cer file to .pem with OpenSSL command line?

To convert a .cer file to .pem using OpenSSL on the command line, first, open a terminal window and navigate to the directory where the .cer file is located. Then, enter the following command:

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

This command tells OpenSSL to read the .cer file in DER format and convert it to a .pem file. The output .pem file will be saved in the same directory as the original .cer file.

Can I convert multiple .cer files at once?

Yes, you can convert multiple .cer files to .pem format at once using a wildcard (*) or by specifying a directory. For example:

openssl x509 -inform der -in .cer -out directory/.pem

This command will convert all .cer files in the current directory that match the wildcard to .pem format and save them in the specified directory.

What is the difference between PEM and DER format?

PEM (Privacy Enhanced Mail) and DER (Distinguished Encoding Rules) are two encoding formats for digital certificates. PEM is a base64-encoded format that uses ASCII characters to encode the certificate, while DER is a binary format that uses a more compact encoding method. Both formats can be used for the same purpose, but PEM is more commonly used and easier to read and manipulate than DER. PEM files are also easier to handle in text-based applications and can be encrypted for added security.