Digital Certificate Formats: SSL Certificate Format Explained

03/08/2023 by admin with 0 comments

Formats of Digital Certificate and How to Change Them

What is a digital certificate?

The validity of a device, server, or user by utilizing encryption and the public key infrastructure (PKI) is confirmed by a digital certificate file or alternatively, an electronic password. To make sure that only reliable people and devices may connect to their networks, organizations can utilize digital certificate authentication. A secure sockets layer certificate, or SSL certificate, is another common use for digital certificates. It allows a web browser to confirm the validity of a website.

The digital certificate provides precise information about the certificate owner’s identity and the certifying authority. Digital certificates can be obtained or converted in a variety of forms. Different certificate types, on the other hand, offer neither advantages or disadvantages.It all relies on the format requirements of the certificate for the programme that will use it.

Certificate encoding schemes and extensions include:


DER: .der, .cer

PKCS#12: .p12, pfx


PKCS#7 .p7c, .p7b

PEM: .crt, .ca-bundle, .pem


Components of a digital certificate

A digital certificate is composed of four components. Owner’s Distinguished Name is at the top, followed by Owner’s Public Key, Issuer’s (CA) Distinguished Name, and Issuer’s Signature.

The digital certificate’s contents are further described in the following list:

Owner’s Distinguished Name (ODN): It is a combination of the owner’s common name and context (position) in the directory tree.

Owner’s Public Key: The receivers decrypt data using the owner’s public key.

Alternate Name for the Subject: This can be an identification like an IP address, email address, fully qualified domain name, etc.

Issue: Digital certificates are issued with an issuance date.

Expiration date: Date on which the digital certificate expires.

Name distinguished by the Issuer: Name distinguished by the Certification Authority.

Digital Signature of the Issuer: A certificate’s issuer’s digital signature is used to verify it.

Types of extensions: Different formats


A PEM (Privacy Enhanced Mail) file is a certificate file with Base64 encoding that is used to confirm the security of websites. It could include a private key, a certificate from a certificate authority (CA) for the server, or other certificates from the trust chain. PEM files are frequently imported from a Unix-based Apache Web server and are compatible with OpenSSL applications.

A text editor can be used to see the contents of a PEM file. There are one or more headers in the file that list the data they contain. The “—-BEGIN CERTIFICATE—-” and “—-END CERTIFICATE—-” statements are present in a certificate’s PEM file.

Private keys and certificates can be sequentially stored in a PEM file. PEM files are often used by Linux and Unix-based web servers. PEM files often include the following extensions:.cer,.pem,.crt, and.key .


A certificate file in binary format is known as a DER (Distinguished Encoding Rules) file. You must view the file using a text editor to distinguish between DER.cer and PEM.cer since DER files can either end in.der or.cer. A DER file shouldn’t contain any BEGIN/END statements since doing so will alter the binary data.

Both private keys and digital certificates can be encoded using the DER format. Java systems frequently employ DER files. The.cer and.der file extensions are frequently used for DER files.


A certificate file that is Base64-encoded is PKCS#7. Private keys cannot be kept in this format. The PKCS#7 file format may only be used to hold digital certificates and Certificate Revocation Lists (CRL).

The “—-BEGIN PKCS7—-” and “—-END PKCS7—-” phrases are found in PKCS#7 files. The.p7b and.p7c file extensions are frequently used with PKCS#7 files. These files are often used by Microsoft Windows and Java Tomcat systems.


Private keys and encrypted private key information can both be included in this format. It often uses a DER or PEM structure, which is subsequently encrypted, to store the data in base64 encoded form. The typical ending is.p8.


The server certificate, intermediate certificate, and private key are all stored in a single binary file format called PKCS#12 that is password-protected. It alludes to a format for exchanging private information. These files are frequently used to import and export certificates and private keys on Windows systems. The.p12 and.pfx extensions are often used.

Conversion of Formats: Changing certificate extension

Your desire to convert your security certificates to another format may be motivated by a variety of factors. One of the causes is that either your system won’t accept the current format or your security certificate file won’t work with the programme. You may simply convert security certificate file types utilizing the most practical and dependable OpenSSL software, no matter why you need to.

Convert CER to PEM

Ubuntu comes pre-installed with the OpenSSL toolkit. In the event that it is not present, you may install it by running crucial instructions in Terminal. Type your sudo password. When given the yes or no choice, choose yes to continue. It will then start installing OpenSSL on the computer.

To convert a CER certificate to PEM, the syntax to be used is:

  • openssl x509 -in cert.cer -out cert.pem.


Convert PEM to CRT:

In order to convert a digital certificate from a pem format to a crt format, the required syntax is:

  • openssl x509 -outform der -in your-cert.pem -out your-cert.crt


Convert CER to PFX:

The process is really straightforward. Without the private key, you can convert a CER certificate to PFX in three easy steps. But since the private key was generated when the CSR (Certificate Signing Request) was established, this operation will need the computer on which it was done. Keep in mind that only the Windows platform will support this technique.

  • Bring the certificate chain into the appropriate shops.
  • In the Windows MMC console, launch the certificate snap-in.
  • From the MMC console, export the certificate in.pfx format.


Certificate file extensions

The label after a file is known as an extension. For instance, a certificate with the name “certificate.cer” has the certificate extension “.cer,” and we added a “*” in front to indicate that the letters in front of the extension type designation might be anything; it is only what comes after the period that counts.

Final thoughts

Depending upon the need and requirement, a user can convert their digital certificate into the required format. For every organization, having a digital certificate is indeed very essential as their fundamental purpose is to ensure that a company’s website is secure from unauthorized access by hackers and thieves. It also establishes secure connections between multiple devices.


Leave Comment