Download GnuPG for your platform:
For Linux it's normally available using your distro's package manager.
After installed, open Kleopatra:
Choose file -> new certificate:
Choose "Create Personal OpenPGP Key Pair":
Fill the form with your seller name and a FAKE OR ANONYMOUS email address (email address can be extracted from your Public Key):
If you leave it with default options you'll get an 2048 bit RSA key good for encrypt and sign.
In the screen you'll be prompted to create a passphrase for your certificate.
It's recommended that you create a backup copy of your certificate:
Next right-click on your new certificate from the list, and choose "Export Certificates...":
You will create an .asc file, after exported open it with a text editor, like notepad
That file will look like this, and that's your public key:
-----BEGIN PGP PUBLIC KEY BLOCK----- Version: GnuPG v2.0.17 (MingW32) mQENBE4LSpABCADjmdEkcUWK8F/N422yJwlqvjJnqEH4ABRlmDFEqO3qIVSa49ES 20Eik3axsFYws2Y0C1/Gue7taoFFgkizoJ6385Pt3DdMJrm+Q8FbAOdk7/i9ltOq gIfC5QCVRl5HGeLqVIkXbDYxLTiRQU+4zZwf0krAesypMPPulkPKs4CBN2r+t7Yj Qn9JZRaTOnW2WF66Dz2whbr9QMHTKYOcjrCuw/LSNljlpzfPoh1/p+J0y0TPsjzZ fwf/XzQ3AA7aYo9ejwsDypfH3XIDv85FLhLXz42M6KrOUXQD8zXblWgBVOQ6YVi3 v9WPDRROa7goc4louxYx7GQ4iRLUrekbkMqLABEBAAG0I1NlbGxlck5hbWUgPHNl bGxlckBibGFja21hcmtldC50b3I+iQE4BBMBAgAiBQJOC0qQAhsPBgsJCAcDAgYV CAIJCgsEFgIDAQIeAQIXgAAKCRAji2WxgPRIoP7dCADKUG0MiCrC8EGXon/e0MkF Jge21p8K9qQWPhkC2+2igqQCrQ1AEl5WRGa2XmhA4rKMCGS8bqQ6EVLIR4lqi6eI sJOoWztC4Vm/0iQDvDqBSMCj7AuaQiT+2PZXdQ978jZM+k4EaVbn+XM3szD0GPsa MPxHn8GiJDjRpZPZYYtHPfduf6WvrEeMXa2Rc86uQ2Jjop3wdDX54O3fTDlIvM9e XAOee18VVcoT0WGztq/Gb82xREcAFe/21huZY0Zntvev8GlgXP46DsOFG3TsxZcy e5vz07UmLLNAwHFIMN+CUDwdEOZZon2OlLMvGfH46F9j9AqhvcM1AGIwSQLSi4jr =SHpw -----END PGP PUBLIC KEY BLOCK-----
Select all, including the headers and footer (those -----BEGIN... and ----END...) and paste it to your Public Key field.