In this article, we will discuss how to convert certificates from the DER format to the PEM format using OpenSSL. The DER format is a binary format, while the PEM format is a base64-encoded format. The PEM format is commonly used for certificates, private keys, and certificate signing requests.

What is OpenSSL?

OpenSSL is a robust, open-source cryptographic toolkit that implements SSL, TLS, and other cryptographic protocols. OpenSSL is widely used for secure communications over the internet and is available for most platforms, including Linux, Windows, and macOS.

What is DER?

DER is an acronym for Distinguished Encoding Rules. It is a binary format used to encode ASN.1 (Abstract Syntax Notation One) data structures. DER is commonly used for certificates, keys, and other cryptographic objects.

What is PEM?

PEM is an acronym for Privacy Enhanced Mail. It is a base64-encoded format used to encode cryptographic objects, including certificates, keys, and certificate signing requests. PEM is widely used in the Unix world and is supported by most web servers, including Apache and Nginx.

Steps to Convert DER to PEM

To convert a certificate from the DER to the PEM format, follow these steps:

Step 1: Install OpenSSL

OpenSSL is not installed by default on most Linux distributions. You can install it by running the following command:

sudo apt-get install openssl

Step 2: Convert the DER Certificate to PEM

To convert the DER certificate to PEM, run the following command:

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

This command instructs OpenSSL to convert the DER certificate (-inform der) to PEM (-out certificate.pem). Replace “certificate.der” with the name of your DER certificate.

Step 3: Verify the PEM Certificate

You can verify the PEM certificate by running the following command:

openssl x509 -in certificate.pem -text -noout

This command will display the contents of the PEM certificate in human-readable format. Verify that the certificate information is correct.

FAQs for openssl convert from der to pem:

What is openssl and why do I need to convert from der to pem?

OpenSSL is an open-source software library that provides tools for implementing Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. Sometimes, you may need to convert a certificate or key file from one format to another format supported by OpenSSL to resolve incompatibility issues in your application. In this case, you may need to convert DER-encoded certificate or key files to PEM-encoded files using OpenSSL.

What is a DER-encoded certificate or key file?

DER stands for Distinguished Encoding Rules, and it is a binary encoding format for X.509 certificates or private keys. DER-encoded certificates and keys are widely used in applications that require secure communication, such as web servers and email clients. However, some applications only support PEM-encoded files, so you may need to convert them to PEM format.

What is a PEM-encoded certificate or key file?

PEM stands for Privacy Enhanced Mail, and it is a format for encoding binary data in ASCII text. PEM-encoded certificates or key files are widely used in Unix-based systems and some Windows-based systems. PEM encoding uses 64-character lines that begin with “—–BEGIN” and end with “—–END”, which makes it easier to transmit and interpret the binary data.

How do I convert a DER-encoded file to a PEM-encoded file using OpenSSL?

To convert a DER-encoded file to a PEM-encoded file using OpenSSL, you need to use the “openssl x509” or “openssl rsa” command for certificates and keys, respectively. For example, to convert a DER-encoded certificate to a PEM-encoded certificate, you can use the following command: “openssl x509 -inform der -in cert.der -out cert.pem”. Similarly, to convert a DER-encoded private key to a PEM-encoded private key, use the command “openssl rsa -inform der -in key.der -out key.pem”.

Can I convert multiple DER-encoded files to PEM format at once?

Yes, you can convert multiple DER-encoded files to PEM format using a batch script or a programming language that supports running command-line shell commands. For example, you can create a batch script that loops through all the DER-encoded files in the directory and converts them to PEM format using the OpenSSL commands mentioned above.

How do I check if a file is in DER or PEM format?

To check the format of a certificate or key file, you can use the OpenSSL “asn1parse” command. If the output shows “DER encoded” or “PEM encoded” in the header section, you can tell the format of the file. Alternatively, you can also open the file in a text editor and check if the file starts with “—–BEGIN” and ends with “—–END”. If it does, it is a PEM-encoded file. If not, it may be in DER format or some other format that is not supported by OpenSSL.