question: Verify the authenticity of the ExpressVPN Linux app with PGP key
answer: 
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  This guide will show you how to verify the authenticity of the app installer for the ExpressVPN app for Linux. This process requires using a system called PGP, which ExpressVPN uses to digitally sign its installers for Linux.
  
  Jump to…
  
  1. Download the PGP key
  2. Verify the fingerprint of the PGP key
  3. Download the app installer and the signature file
  4. Verifying the signature on an installer