As of 1993, Tempest ATs were already on the surplus market and Computer Reset in Texas (of LGR fame) was reselling them as what they called "a spy-proof relic of the Cold War", for $999 including 640K RAM, two floppy drives, two cartridge drives, and the keyboard. You could also get the matching Tempest 5151 monochrome monitor for $159.

I just watched a 2.5hr FOIA request and I’m not mad about it.

For anyone who may be entertained by the following information, the problem with the lid and with long slits isn't that the radio waves can "fit through" the very narrow gap...  The problem is that radio waves are blocked by eddy currents in the shielding.  The incoming radio wave pushes on the electrons of the conductor, they move in step with the radio wave, and this produces an exactly opposite wave that serves to completely cancel the original (from the perspective of someone outside the case - inside the case, the new wave looks like a reflection, which I suppose it is).  When you cut a slit in the material, or fasten two pieces together with a tiny gap between them, this blocks the eddy currents, and when it gets to a significant fraction of a wavelength it allows the radio waves to go through the metal on either side of the slit.  Tightening the screws on the lid reduces the resistance between the lid and the front panel, allowing more eddy current to flow, making the cancellation closer to total.  I don't know anything about tempest hardening, but in the industrial sector, when it's necessary to provide serious shielding, it's standard practice to use both RF-absorbing and RF-reflecting materials.  I didn't see anything in your machine that seemed like it was designed to absorb energy.

As an RF engineer, this is actually a pretty fantastic introduction to the concepts of EMI protections and the thought that goes into building products to certain compliance specs. I can't pick anything out that seemed glaringly untrue. Nice job as always!

As a guy from Spokane you mentioning Taco Time activated me like a freaking sleeper agent

As an engineer involved with RF,RFI and TEMPEST, this was by far the besr video about the subject made for a non-expert audience. Congratulations!

re: the intro, i was given a PC as a teenager by someone who took it home from an RAF office (with permission). it had 3 accounts: administrator, support, and user. each account had a picture of an RAF plane (typhoon, vulcan, and harrier). no prizes for guessing the passwords

25 years ago or so I was volunteering at a charity that recycled PCs from businesses and we'd regularly get stacks of PCs in with CSE (the Canadian NSA equivalent) stickers on them saying "TEMPEST CERTIFIED" (or something to that effect).

I didn't expect to see a 2.5h video today on this topic... but here we are!

Thanks for doing this one. Keeping that bar set high on quality!

Every time I watch one of these, CRD insists that the topic is dry and uninteresting in some way. Then I watch it and it's the most interesting stuff.

I worked at a DoD contractor for several years, Ethernet cables that are in classified systems/networks have a special metal timeout box they live in before being considered clear.  There's wild rules around peripherals like keyboards and mice too

This brings me back.... by the time I joined the Marines, my little ISMO office was flying Zenith Z-248s which were also Tempest certified. There was a van that went around to bases demonstrating the need for Tempest - they could show keyboard output of an unprotected PC 100ft away, through walls. Same for video. Signals Intelligence was a thing. I spent my last year overseas... in Okinawa, our RASC (Mainframes) sat near a seaport (Naha), and a Russian "fishing trawler" sat permanently docked, with a very impressive set of antennas pointed directly toward Camp Kinser and our RASC. The "flying" is a reference... the ISMO office was at an Air Station, and at a unit training exercise, an instructor asked my gunny what we flew - "Z-248s" was his response.

I suspect at least a partial (and somewhat disappointing) reason why we've not really seen any major real-life instances of compromise as a result of EMR, is largely because we have better, simpler, and cheaper ways to accomplish the same goals. Why go through all the effort to capture and decode the signals when you can trick, coerce, or bribe employees/agents to give up the information willingly.

Sadly those don't have cool technical solutions worthy of a 2 and a half hour video.

I screamed so loud when the history with Max Miller hardtack clip showed up. I wasn't expecting that although I should have given the channel I'm on. Deep dives into niche topics are both channels bread and butter

1:06:51 This is a long comment, apologies. I worked for many years in military aerospace where EMR and the subsequent EMI are environment hazards, not necessarily for secrecy concerns, but because you're in a tiny metal tube with extremely sensitive equipment everywhere. Consider an AWACS or AEW&C aircraft, where EMR needs to be tightly controlled to not impact instrumentation, most of which are radio based.

I use the term "permeability" here which means sort of "how well does this thing conduct magnetically". Air (or a vacuum) has a permeability of 1, as does aluminum roughly. Copper is just shy of 1. Steel all over the place, from hundreds to thousands. The big tl;dr here is that the closer to 1 you are, the more magnetic waves just pass through the material rather than being distorted or concentrated by it. Separately, a material's bulk conductivity determines how well it absorbs and reflects RF energy via eddy currents, and that's the property that actually matters for shielding.

Steel is a nightmare material in this regard. Its permeability changes with the intensity of the internal field strength; it "remembers" prior magnetization; welding, bending, machining, forming, work hardening, etc. change the grain structure in any given area its done and modify its permeability in ways that are nearly impossible to characterize; its permeability falls off with frequency; and lastly its permeability swings with temperature.

On the other hand, aluminum has well characterized conductivity. You can bend it, weld it, form it, stress it, shape it however you need, and the simulations play out the same. (Massive asterisk but here that's true enough) It can be hot. It can be cold. You can leave it in heavy field strength environments for decades and its relative permeability and bulk conductivity won't change. Its skin depth and shielding at given frequencies are easily predictable.

Aluminum's stable, predictable conductivity gives well-characterized attenuation across a wide RF band, and you have sort of a wonder material in this context.

I'm so glad you made this video!
I had a Delta Data Tempest PC floating around for years and never could come up with a good way to demonstrate the capabilities of the design. You did it proper justice!

Also, no need to worry about finding scary data, I recently found a bunch of nuclear data from Los Alamos on my 1963 LGP-21 and no one's come busting the doors down yet, so I think you're good, haha.

The manner by which you demonstrate how trivial EM leaks are to pickup, both the obvious monitor Van Eck phreaking and the more subtle way I won't spoil are maybe the best example of this I've ever seen. Thank you dude

40:00 I'm surprised you didn't mention your early video about the NES being essentially a TV station during this segment, since iirc you managed to actually pick up the RF video signal wirelessly. That was the first video of yours I ever saw, and I think it was for a lot of other people too, so it would have been a neat callback 🙂

Yet another banger from Cash Register Dude! I guess he’s pivoting into non register content  now!

Radio nerd here. A big problem these days are electronics that had no certification or testing done and were flooded onto the market regardless, usually through sources that bypass testing like Amazon or Aliexpress. A huge pain in our collective butts are switch-mode power supplies, the sort you'd find in wall power bricks and USB adapters and the like. Some of them emit such horrendous EMI that my antenna can pick them up from neighbours several houses down. We also have a drill battery charger which emits a very broad-spectrum wall of oscillating noise from around 100mhz to 250mhz, which is just bonkers.

And yes, just by casually observing these noise patterns you can, with enough time, deduce what is going on in the world around you. I can "hear" when my neighbour's motion lights turn on, when they use their TV, when they have their laptop open, etc. And that's just by observing noise patterns, not even getting into decoding or demodulating any actual signals. EMI is a serious issue and it seems like so many electronics have just stopped caring about it.

Fun story about SCIFs.  They can also be whole buildings.  I was a grad student working for a ONR grant, and had to go to a conference at such a facility once.  I didn't have my clearance at the time, so I was allowed in the building, but I had to be escorted at all times, and was only allowed to see non-secret talks.  When there was a secret talk, me and the one other person without a clearance were escorted to another SCIF inside the building where we were left alone.  Essentially, the SCIF within the SCIF (the building) allowed us to be present within a secure environment while they relied on the shielding of the inner SCIF to protect the remainder of the building.