Understanding the Difference Between Certificate Formats
Certificates play a crucial role in securing data transmission over networks. They are used to authenticate the identity of parties involved in a communication and to encrypt data being transmitted. Different types of certificates exist, including .pem, .cer, and .pfx. Each certificate format has a different structure and encoding, and as such, they are not directly compatible with one another. This means that if you need to convert a certificate file from one format to another, you will need to use a conversion tool like openssl.
What is a .cer Certificate File?
The .cer file extension is used to denote a certificate file that contains public key information about a website or organization. It is often issued by a certificate authority and is used to identify a website or organization and to provide a secure connection for online transactions.
What is a .pem Certificate File?
A .pem certificate file is a base64 encoded certificate that contains both the public key and private key of a website or organization. It is often used in web servers to provide secure connections over HTTPS.
The Basics of openssl Command Line Tool
OpenSSL is a command-line tool that is used to manipulate SSL/TLS certificates. It is widely used in Linux and Unix systems for various cryptographic operations. The openssl command can be used to view, manipulate, and convert certificate files.
Installing openssl on Ubuntu
To install openssl on Ubuntu, you should first update the package index and then install the openssl package using the apt package manager.
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Converting a .cer Certificate File to .pem Format
To convert a .cer certificate file to .pem format using OpenSSL, you should use the following command:
openssl x509 -inform der -in certificate.cer -out certificate.pem
This command specifies that the input format is der and the input file is certificate.cer. The output file is specified as certificate.pem.
Converting a .pfx Certificate File to .pem Format
Another common certificate format is the .pfx certificate file. The .pfx file extension is used to denote a certificate file that contains both the public and private key of a website or organization. It is often used in Microsoft Windows systems.
To convert a .pfx certificate file to .pem format using OpenSSL, you should use the following command:
openssl pkcs12 -in certificate.pfx -out certificate.pem -nodes
This command specifies that the input file is certificate.pfx, and the output file is certificate.pem. The -nodes option tells OpenSSL not to encrypt the output file with a password.
Converting a .pem Certificate File to .cer Format
To convert a .pem certificate file to .cer format using OpenSSL, you should use the following command:
openssl x509 -in certificate.pem -outform der -out certificate.cer
This command specifies that the input file is certificate.pem, and the output format is der. The output file is specified as certificate.cer.
FAQs for convert certificate cer to pem openssl
What is a certificate and why do I need to convert it?
A certificate is a digital document that verifies the identity of a website or server. It is important to convert a certificate because different applications require different formats. For example, .cer is a format used by Microsoft, while .pem is used by OpenSSL.
What is OpenSSL?
OpenSSL is a popular open-source cryptographic library that is used to secure communications over computer networks. It supports a wide range of cryptographic algorithms and protocols.
How do I convert a certificate cer to pem openssl?
To convert a certificate from .cer to .pem using OpenSSL, you can use the following command:
openssl x509 -inform der -in certificate.cer -out certificate.pem
This command will convert the certificate from binary (DER) format to base64 (PEM) format. Note that you will need to replace “certificate.cer” with the filename of your certificate.
Are there any other ways to convert a certificate from cer to pem?
Yes, there are other ways to convert a certificate from cer to pem. Some certificate authorities provide online tools for converting certificates, and there are also third-party tools available for download. However, using OpenSSL is one of the most popular and reliable methods.
Can I convert multiple certificates at the same time?
Yes, you can use a wildcard to specify multiple certificates in one command. For example,
openssl x509 -in *.cer -outform PEM -out certificates.pem
This command will convert all .cer files in the current directory to .pem format and save them in a single file called “certificates.pem”.