OpenSSL is a versatile and widely used open-source software library that provides support for SSL and TLS protocols. It is commonly used for generating and manipulating various cryptographic keys, certificates, and various other cryptographic operations. One of the operations that OpenSSL can perform is converting a public key from PEM to DER format. In this essay, we will explore the steps involved in this process and discuss why it is necessary.

PEM vs. DER

Before we dive into the process of converting a public key from PEM to DER format, let’s first understand the difference between the two formats. PEM (Privacy Enhanced Mail) is a base64-encoded format that is commonly used for encoding and storing X.509 certificates, public, and private keys. PEM files are human-readable, and they usually have extensions like .pem, .crt, .cer, .key, etc.

On the other hand, DER (Distinguished Encoding Rules) is a binary format that is used for encoding X.509 certificates, public, and private keys. DER files are not human-readable, and they usually have extensions like .der and .cer.

Why Convert from PEM to DER?

The need to convert a public key from PEM to DER format arises when applications or systems require different key formats. For example, if you want to use a public key in a Java-based application, you need to convert it to DER format since Java uses DER-encoded keys. Similarly, if you want to use a public key in a C or C++ application, you might need to convert it to DER format since these programming languages often use DER-encoded keys.

Converting a public key from PEM to DER format using OpenSSL is a necessary process when different applications and systems require different key formats. PEM is a base64-encoded format that is human-readable, while DER is a binary format that is not human-readable. OpenSSL provides a simple command-line interface to convert a public key from PEM to DER, and there are additional options available to customize the process. Additionally, OpenSSL can perform various other cryptographic operations, such as generating private keys, creating self-signed certificates, and encrypting and decrypting files.

Converting a Public Key from PEM to DER

Now that we have understood the difference between PEM and DER formats and why we need to convert a public key from PEM to DER, let’s dive into the process of converting. The following steps outline the process:

  1. Open a terminal or command-line interface.
  2. Navigate to the directory containing the PEM-encoded public key file.
  3. Run the following OpenSSL command to convert the PEM-encoded public key to DER format:

“`bash

“`

In the above command, replace “public_key.pem” with the name of your PEM-encoded public key file, and “public_key.der” with the name of the file you want to save the DER-encoded public key to.

  1. Press Enter to execute the command.
  2. Verify that the DER-encoded public key file has been created in the same directory.

That’s it! You have successfully converted a public key from PEM to DER format.

Converting a public key from PEM to DER format using OpenSSL is necessary when applications or systems require different key formats. PEM is a human-readable base64-encoded format, while DER is a binary format. To convert a public key, navigate to the directory containing the PEM-encoded public key file, run the OpenSSL command to convert it to DER format, and verify that the DER-encoded public key file has been created in the same directory. Additional options can be used to customize the process according to your needs. OpenSSL can also be used for other cryptographic operations like generating a private key, generating a self-signed certificate, and encrypting and decrypting files.

Additional Options

There are a few additional OpenSSL options that you can use while converting a public key from PEM to DER format. These options can help you customize the process according to your needs. Here are some of the options and their usage:

  • -inform PEM: This option specifies the input format as PEM. This is the default input format for the OpenSSL command-line tool, so you can omit this option if your input file is in PEM format.
  • -outform DER: This option specifies the output format as DER. This is necessary if you want to convert your public key to DER format.
  • -in: This option specifies the input file name.
  • -out: This option specifies the output file name.

Other OpenSSL Operations

OpenSSL is a versatile tool that can be used for various cryptographic operations. Here are some of the other operations that you can perform using OpenSSL:

Generating a Private Key

You can use OpenSSL to generate a private key using the following command:

In the above command, replace “private_key.pem” with the name of the file you want to save the private key to. You can also replace “RSA” with other algorithms like “EC” (elliptic curve) or “DSA” (Digital Signature Algorithm).

Generating a Self-signed Certificate

You can use OpenSSL to generate a self-signed certificate using the following command:

In the above command, replace “private_key.pem” with the name of the file containing the private key that you generated earlier, and “certificate.pem” with the name of the file you want to save the self-signed certificate to. You can also change the number of days that the certificate is valid for by replacing “365” with the number of days you want.

Encrypting and Decrypting Files

You can use OpenSSL to encrypt and decrypt files using various encryption algorithms like AES, DES, etc. Here is an example of how to encrypt a file using OpenSSL:

In the above command, replace “file.txt” with the name of the file you want to encrypt, and “file.enc” with the name of the file you want to save the encrypted file to. You can also change the encryption algorithm by replacing “aes-256-cbc” with other algorithms like “des3” (Triple DES).

FAQs – openssl convert public key from pem to der

What is openssl?

OpenSSL is an open-source cryptographic library that provides a set of functions for many secure communication protocols, such as TLS, SSL, and cryptographic algorithms. This library is widely used by many software programs to provide security for data transmission and storage.

What is a public key?

In a cryptographic system that uses asymmetric cryptography, a public key is one of a pair of keys that are used for encryption and decryption. The public key is made available to anyone who wants to send an encrypted message to the owner of the private key.

What is a PEM file?

PEM stands for Privacy Enhanced Mail format, which is a file format that is used to store cryptographic keys in a text-based format. It is often used to store SSL and TLS certificates and private keys, as well as other types of cryptographic information.

What is a DER file?

DER stands for Distinguished Encoding Rules, which is a binary format that is used to store cryptographic keys. It is a more compact format than PEM and is often used in applications that require smaller file sizes.

How to convert a public key from PEM to DER using OpenSSL?

To convert a public key from a PEM file to a DER file using OpenSSL, you can use the following command:

openssl x509 -inform pem -in publickey.pem -outform der -out publickey.der -pubkey

This command will read in the public key from the PEM file named ‘publickey.pem’, convert it to DER format, output the result into a file named ‘publickey.der’, and also output the public key in PEM format to the console.

Are there any security risks associated with converting a public key from PEM to DER?

No, there are no security risks associated with converting a public key from PEM to DER. The main purpose of converting a public key from one format to another is to meet the requirements of a specific software application. The security of the public key is not affected by the format in which it is stored.