Working with an Online and Offline Computer when using GnuPG - Best Practice?

Robert J. Hansen rjh at
Wed Oct 11 04:49:57 CEST 2017

>> The point of using the
>> old photoreceptor was that way we were dead certain there was no
>> exploitable integrated circuit in the photoreceptor...
> I don't really see the point of purposely reducing the bitrate of a
> serial link.

Supply chain security.  The more complicated the hardware, the harder it
is to prove the ICs and firmware haven't been exploited.  If you're
using hardware you scavenged from a ham radio swap meet, you can be
pretty sure there's nothing malicious in the hardware.

Our use case was a vote tabulating system communicating realtime updates
with a publicly-facing web server.  The assumption was the web server
was compromised: given that, how can you be absolutely sure there's no
communication channel back to the trusted tabulator?

Answer: a 1960s photoreceptor.

We didn't need a fast link from the tabulator to the web server: we
needed a slow and absolutely, positively, definitively one-way link.

More information about the Gnupg-users mailing list