How to generate a 1024 bit DKIM key in cPanel

Introduction

By default, cPanel generates 2048-bit DKIM keys, which are more secure than 1024-bit keys. However, while unsupported, it is possible to generate a 1024-bit DKIM key in cPanel.

Please note that we do not advise that you reduce the security of any aspect of your server, including making less secure DKIM keys. 

Procedure

1. Access the server's command line as the 'root' user via SSH or "Terminal" in WHM.
2. Open /usr/local/cpanel/Cpanel/RSA/Constants.pm in your preferred text editor.
3. Locate the following line.

       $DEFAULT_KEY_SIZE = 2048;

4. Change the value to 1024.

       $DEFAULT_KEY_SIZE = 1024;

5. Save the changes and exit the text editor.
6. Use the dkim_keys_uninstall script to uninstall the DKIM keys for the cPanel user.

   /usr/local/cpanel/bin/dkim_keys_uninstall $USERNAME

   Please note that "$username" must be replaced with the cPanel user's username.
7. Use the dkim_keys_install to reinstall the DKIM keys.

   /usr/local/cpanel/bin/dkim_keys_install $USERNAME

   Please note that "$username" must be replaced with the cPanel user's username.