The formal development of secure systems (my 1992 doctoral thesis)

Since this doesn't seem to be findable online anywhere here's a PDF generated from the original .tex files that I kept on a floppy for 30 years!

If you're curious about formal methods and computer security in 1992, or just want to read some CSP and occam code, you may enjoy it. It does get a little technical:

Taschen, Acorn and Knoll's Law

I have a copy of Taschen's huge book The Computer. 472 pages of computer history with lots of lovely photographs.

Which is great, except that I turned to the page that covers one of the computers I know well, the BBC Micro, and see this:

Which, at first glance, look fine, or rather it doesn't. The machine on the right is not an "Acorn BBC Micro, 1981", it's an "Acorn BBC Master 128, 1986". Sure, it's part of the BBC Micro line of computers but it's not what the caption says.

So now I'm stuck looking at the book thinking about Knoll's Law of Media Accuracy: "Everything you read in the newspapers is absolutely true except for the rare story of which you happen to have firsthand knowledge."

PS Also, I'd argue that Acorn did "stand a chance in the face of competition from Silicon Valley" because it pivoted (as the Silicon Valley types like to say) into Arm.

The Acme Klein Bottle (from Cliff Stoll and family)

Cliff Stoll (who is probably most famous for writing the wonderful Cuckoo's Egg about tracking a hacker when doing so was almost recreational) runs a business making Klein bottles: Acme Klein Bottle. A Klein bottle is a weird shape (that doesn't actually exist in three dimensions) with only one side. A bottle with no inside and outside. A bit like the Möbius strip has only one side.

In fact a Klein bottle can be made from two Möbius strips glued together along their edges. Unfortunately, that doesn't actually work in three dimensions so we're left with doing something called "immersing" the bottle in our three dimensional world.

The result is the bottle has to intersect itself. And that's what Cliff Stoll sells: immersions of Klein bottles in three dimensions. The real Klein bottle would need an extra dimension to not intersect itself. Here's my Acme Klein Bottle:

Cliff has a whole page describing the properties of a Klein Bottle. It's worth a read. Buying from Cliff is an experience in itself. Here's the packaging mine came in:

Plus it comes with a free slide rule (every detail of every document included is worth reading):

Inspection report:

Safety instructions:

For best results, avoid doing stupid things.

And there are some stickers, and a graduated scale you can add to the bottle (plus Cliff threw in a punched card to use as a bookmark):

So, if like me you were tired of the Möbius strip being the only non-orientable surface you have in your home, rush over to Acme Klein Bottle and peruse the fine selection of bottles, large and klein, at Acme Klein Bottle.

I haven't described all that comes in the package, or what communication with Cliff via email is like. But if you want an experience that ends with a Klein bottle in your home, buy one.