Postcard from Tempest

Many years ago I worked for a mainframe manufacturer in the UK. In the late 70s when they bought out a new, cuter, faster range of machines, I got trained up as an operations and security consultant. Shortly after that, I joined a project to install a pair of the mainframes for one of the many government departments that went for the new equipment.

The machines were put together from sets of parts produced all over the UK and then commissioned. The commissioning site was an old iron works in Manchester, so that's where I went for a few months. The first conversation with the project manager in Manchester was an introduction to all sorts of things I knew nothing about. There was something called Tempest the existence of which was covered by the Official Secrets Act at the time.

When electricity moves along a wire, it generates radio waves, and these can be detected and recorded. With the right equipment and a lot of work, you can determine what the computer was doing. I had enough physics background to grasp the principles, but I could see that it wouldn't be easy. Tempest referred to this information leakage, and the possibility of screening an area against it. During that first week, I was asked if I'd like to spend some time in a salt mine in Cheshire! I learned that the company had a Tempest testing environment in the mine because it was electrically quiet down there. It was an interesting idea, but I still said no.

Instead, I helped the engineers get the mainframes ready for testing and shipping. I did the software installation and ran through the test suite to make sure it was all OK, then installed the security packages over the top and did another set of tests. This was back in the Coloured Book days of IT security, and the company claimed that their mainframes, correctly set up could achieve B2 security.

That was something the customer took really seriously, and I think we came pretty close.

Back on the customer site, I watched a Tempest screened machine room being built, something that I found fascinating. Then 5 trucks arrived with the equipment, and it got unloaded and set up, and all the testing was done again.

The on-site operations team got trained by several of us, and handover was complete. All in all I spent close to 18 months on the project, one of the most impressive projects I've worked on over the years.

I don't know when Tempest was first mentioned in public, but as with so many things once held secret, it's openly discussed on Wikipedia.

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