Don't need to break encryption when you can just essentially "look over their shoulder" while they read it.
The solution to that is so simple... stop being lazy. Use a "digital airlock".
Download the encrypted file, copy to a storage device, open and decrypt in a virtual machine on a secured computer with no wireless capability and never connected to the internet, wipe or destroy when finished.
The spook would need to be physically present at the computer to view the encrypted data.