Understanding PEM and OpenSSH Formats

Before we dive into the process of converting PEM to OpenSSH, let’s first take a closer look at the two formats. PEM, or Privacy Enhanced Mail, is a base64-encoded format that is used to store SSL/TLS certificates and private keys. OpenSSH, on the other hand, is a suite of network connectivity tools that use the SSH protocol. OpenSSH is primarily used for remote login and file transfer over an encrypted connection.

What is PEM Format?

PEM format is commonly used to store SSL/TLS certificates and private keys. PEM files are base64-encoded ASCII files that start with “—–BEGIN” and end with “—–END” statements. A PEM file can contain a single certificate or a chain of certificates. PEM files can also store private keys in encrypted form.

What is OpenSSH Format?

OpenSSH is a suite of network connectivity tools that use the SSH protocol. OpenSSH client and server applications can be used to establish secure remote connections between two systems. OpenSSH uses a proprietary format to store public and private keys.

Converting PEM to OpenSSH

Converting PEM to OpenSSH format is a simple process that can be done using the OpenSSL command-line tool. OpenSSL is a widely-used cryptographic library that provides support for various cryptographic functions. Here are the steps to convert a PEM file to OpenSSH format:

1. Convert PEM to DER format using OpenSSL:
   “`

2. Convert DER to OpenSSH format using ssh-keygen:

FAQs – Convert PEM to OpenSSH

What is a PEM file?

A PEM (Privacy Enhanced Mail) file is a commonly used file format for storing cryptographic keys, certificates, and other sensitive information. It uses a Base64 encoding for the binary data, which is then wrapped in a PEM header and footer. PEM files are commonly used by OpenSSL and are typically used to store private keys and x.509 certificates.

What is an OpenSSH file?

OpenSSH is a widely used implementation of the SSH protocol. It is used to remotely connect to servers and transfer files securely. The OpenSSH format is different from the PEM format, and uses a binary (not human-readable) format. OpenSSH files typically have file extensions of .pub for public keys and no extension for private keys.

Why would I need to convert a PEM file to OpenSSH?

You may need to convert a PEM file to OpenSSH format if you want to use the file to connect to a server with OpenSSH. For example, if you have a private key in PEM format that you need to use to authenticate to an OpenSSH server, you will need to convert it to the OpenSSH format (which has no extension) before using it.

How do I convert a PEM file to OpenSSH?

To convert a PEM file to OpenSSH format, you can use the ssh-keygen utility, which is included with most Unix-based systems (including macOS and Linux). To convert a PEM file to OpenSSH format, run the following command:

ssh-keygen -p -m PEM -f /path/to/key.pem

This will prompt you to enter the passphrase for the key, and then will convert it to OpenSSH format, saving the new key to the file /path/to/key.

Can I convert an OpenSSH file to PEM format?

Yes, you can convert an OpenSSH file to PEM format using the same ssh-keygen utility. To convert an OpenSSH private key to PEM format, run the following command:

ssh-keygen -p -m PEM -f /path/to/key

This will prompt you to enter the passphrase for the key, and then will convert it to PEM format, saving the new key to the file /path/to/key.pem.