Understanding the Basics of OpenSSH Public Key and PEM

OpenSSH Public Key and PEM are two of the most commonly used cryptographic protocols in Linux. An OpenSSH public key is used to authenticate a user, while PEM is a file format used to store cryptographic keys. Converting an OpenSSH public key to PEM is a relatively simple process that can be done using OpenSSL commands.

Why Convert an OpenSSH Public Key to PEM?

There are many reasons why you might need to convert an OpenSSH public key to PEM. For example, if you want to use an OpenSSH public key in a tool that only supports the PEM file format, you’ll need to convert it first. Additionally, converting an OpenSSH public key to PEM can make it easier to use with other tools and services.

Converting an OpenSSH Public Key to PEM using OpenSSL

To convert an OpenSSH public key to PEM, you’ll need to use OpenSSL. Here’s how to do it:

  1. First, copy the OpenSSH public key to your local machine. You can do this by running the following command:

“`
$ scp username@remote-host:/path/to/public/key.pub /path/to/local/

  1. Once you have the key on your local machine, convert it to PEM using the following command:

$ ssh-keygen -f /path/to/local/key.pub -e -m pem > /path/to/local/key.pem

  1. Finally, you can verify that the key has been converted by opening the PEM file in a text editor and ensuring that it begins with “—–BEGIN PUBLIC KEY—–” and ends with “—–END PUBLIC KEY—–“.
One key takeaway from this text is that converting an OpenSSH public key to PEM is a simple process using OpenSSL commands. This conversion allows the key to be used with tools and services that only support the PEM file format, making it easier to secure network communications and authenticate users. It’s important to follow best practices for key management, including storing keys in a secure location, rotating them regularly, and revoking them immediately if they are compromised. Additionally, secure key exchange protocols like Diffie-Hellman or Secure Shell should be used to exchange keys without revealing them to third parties, and Public Key Infrastructure (PKI) can be used to manage the creation, distribution, and revocation of keys.

Additional Options

There are a few additional options you can use when converting an OpenSSH public key to PEM using OpenSSL. For example, you can use the -i flag to specify the input file format (e.g. OpenSSH), and the -o flag to specify the output file format (e.g. PEM). You can also use the -f flag to specify the input file, and the -m flag to specify the output format (e.g. pem).

Using the Converted PEM File

Once you have converted your OpenSSH public key to PEM, you can use it with a wide range of tools and services that support the PEM file format. For example, you can use it with OpenSSL to sign and verify messages, or with TLS/SSL to secure network communications. You can also use it with cloud services like AWS and GCP, which often require PEM-formatted keys for authentication.

Best Practices for Key Management

It’s important to follow best practices when managing cryptographic keys, including OpenSSH public keys and PEM files. For example, you should always store keys in a secure location, and restrict access to them only to authorized individuals. You should also rotate keys regularly, and revoke them immediately if they are compromised.

Secure Key Exchange

When exchanging keys, it is important to do so securely. One way to do this is to use the Diffie-Hellman key exchange protocol, which allows two parties to exchange keys without revealing them to a third party. Another option is to use the Secure Shell (SSH) protocol, which provides secure communication over an unsecured network.

Public Key Infrastructure (PKI)

In many organizations, the management of cryptographic keys is done using a Public Key Infrastructure (PKI). A PKI is a system that uses digital certificates and a Certificate Authority (CA) to manage the creation, distribution, and revocation of keys. PKI is used to secure email, web servers, and other applications that require secure communication.

FAQs for converting OpenSSH public key to PEM

What is an OpenSSH public key?

An OpenSSH public key uses the SSH (Secure Shell) protocol to authenticate and encrypt data between two systems. It is used to establish a secure connection between a client and a server.

Why do I need to convert an OpenSSH public key to PEM?

A PEM (Privacy Enhanced Mail) encoded file is a widely used format for storing and sharing public keys, particularly in web services and SSL/TLS certificates. If you need to use an OpenSSH public key in a system that requires PEM format, you will need to convert it.

How do I convert an OpenSSH public key to PEM?

To convert an OpenSSH public key to PEM, you can use the ssh-keygen command line tool which is available on most UNIX-like systems. Simply run the following command:
ssh-keygen -f -e -m pem > where <openssh.key> is the filename of the OpenSSH public key, and <pem.key> is the desired filename of the PEM formatted public key.

Can I convert multiple OpenSSH public keys to PEM at once?

Yes, you can convert multiple OpenSSH public keys to PEM at once by using a loop in the command line. For example:
for file in *.pub; do ssh-keygen -f “$file” -e -m pem > “${file%.pub}.pem”; done
This command will convert all the .pub files in the current directory to PEM format.

What should I do after converting an OpenSSH public key to PEM?

After converting an OpenSSH public key to PEM, you can use it in any system that accepts PEM format. Just be sure to safeguard the private key that corresponds to the public key, as it is the only means of decrypting messages encrypted with the public key.