Understanding the Basics of PEM and PPK

Before we dive into the process of converting PEM to PPK, let’s understand what these file formats are. PEM is a Base64 encoded format that represents a certificate, public key, or private key. It’s widely used in Unix-like systems and is supported by most web servers. PPK, on the other hand, is a PuTTY Private Key file format used for SSH authentication. It’s a proprietary format used by PuTTY, a popular SSH client for Windows.

Why Convert PEM to PPK?

If you’re working on a Windows machine and need to connect to a Unix server, you’ll need to use an SSH client like PuTTY. But PuTTY doesn’t support PEM files, only PPK files. That’s why you need to convert PEM to PPK.


Before we begin with the conversion process, make sure you have OpenSSL installed on your machine. You can check if it’s already installed by running the following command in your terminal:

If OpenSSL is not installed, you can install it using your operating system’s package manager.

Converting PEM to PPK

Now that you have OpenSSL installed, let’s move on to the conversion process. Follow these steps:

Step 1: Generate a Private Key in PEM Format

If you already have a private key in PEM format, you can skip this step. Otherwise, run the following command to generate a private key in PEM format:

This command generates a new 2048-bit RSA private key and saves it in a file named private_key.pem.

Step 2: Convert PEM to PPK

To convert the private key from PEM to PPK format, run the following command:

This command uses PuTTYgen, a tool that comes with PuTTY, to convert the private key from PEM to PPK format. It reads the private_key.pem file and creates a new file named private_key.ppk in PPK format.

Step 3: Test the PPK File

To make sure the conversion was successful, test the new PPK file by connecting to the server using PuTTY. Open PuTTY and navigate to Connection > SSH > Auth. Click on the Browse button next to “Private key file for authentication” and select the new private_key.ppk file. Now try to connect to the server. If the connection is successful, you’ve successfully converted PEM to PPK.

FAQs for openssl convert pem to ppk

What is OpenSSL?

OpenSSL is a security tool, an open-source implementation of the SSL and TLS protocols, widely used for secure communication over the internet. It provides cryptographic functions, including private/public key signing, encryption, and verification. OpenSSL is available on most Unix and Linux-based systems and is considered standard in many network applications.

What is a PEM file?

PEM stands for Privacy-enhanced Electronic Mail, a base64-encoded text file that contains a digital certificate or keys, usually in ASCII format, used to secure communications over the internet. A PEM file may contain different types of keys, such as RSA or ECDSA. Some examples of PEM files are server or client certificate files, CA (certificate authorities) files, or key files.

What is a PPK file?

PPK stands for PuTTY Private Key, a format used by PuTTY, a popular SSH and telnet client program for Windows. PPK files are the default private key format used by PuTTY, the software creates these files when you generate a new key pair. PPK files are used to authenticate SSH or SFTP sessions to remote servers. PPK files are not compatible with OpenSSH or OpenSSL.

How can I convert a PEM file to a PPK file using OpenSSL?

To convert a PEM file to a PPK file using OpenSSL, you need to use the following command:

openssl pkcs8 -topk8 -inform PEM -outform PUTTY -in key.pem -out key.ppk

This command converts the private key from PEM format to PuTTY format using the pkcs8 utility. The -topk8 option specifies that PKCS#8 format is used to store the private key. The -inform option specifies the input format (PEM) and -outform specifies the output format (PuTTY). Finally, the -in and -out options specify the input and output filenames, respectively.

Are there other ways to convert a PEM file to a PPK file?

Yes, there are other tools available to convert a PEM file to a PPK file, such as PuTTYgen, a graphical user interface for managing SSH keys, or WinSCP, an SFTP and SCP client for Windows that includes a key generator tool. These tools can generate PPK files directly, without using OpenSSL. However, if you prefer to use OpenSSL, the command we mentioned earlier is a quick and easy way to convert a PEM file to a PPK file.

Can I convert a PPK file to a PEM file?

Yes, you can convert a PPK file to a PEM format using PuTTYgen or the putty-keygen utility, which comes with PuTTY. PuTTYgen allows you to load a PPK file, and then export it as a PEM file, using the “Save private key” or “Save public key” options. Alternatively, you can use the following command to convert a PPK file to a PEM file using putty-keygen:

puttygen key.ppk -O private-openssh -o key.pem

This command converts the private key in PPK format to OpenSSH format, which is equivalent to PEM format. The -O option specifies the output format, and the -o option specifies the output filename.