Visual Cryptography For Physical Keyrings

Visual cryptography is one of those unusual cases that kind of looks like a good idea, but it turns out is fraught with problems. The idea is straightforward enough — an image to encrypt is sampled and a series of sub-pixel patterns are produced which are distributed to multiple separate images. When individual images are printed to transparent film, and all films in the set are brought into alignment, an image appears out of the randomness. Without at least a minimum number of such images, the original image cannot be resolved. Well, sort of. [anfractuosity] wanted to play with the concept of visual cryptography in a slightly different medium, that of a set of metal plates, shaped as a set of keyrings.

Two image ‘share pairs’ needed as a minimum to form an image when combined

Metal blanks were laser cut, with the image being formed by transmitted light through coincident holes in both plate pairs, when correctly aligned. What, we hear you ask, is the problem with this cryptography technique? Well, one issue is that of faking messages. It is possible for a malicious third party, given either one of the keys in a pair, to construct a matching key composing an entirely different message, and then substitute this for the second key, duping both original parties. Obviously this would need both parties to be physically compromised, but neither would necessarily notice the substitution, if neither party knew the originally encrypted message.  For those interested in digging in a little deeper, do checkout this classic paper by Naor and Shamir [pdf] of the Wiezmann Institute. Still, despite the issues, for a visual hack it’s still a pretty fun technique!

Want to learn a little more about crypto techniques you can do at home? Here’s our guide. Encryption too hard to break, but need a way to eavesdrop? Just punt out a flawed system, and you’re good to go.

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This Spherical Lamp’s Pieces Ship Flat, Thanks To Math

[Nervous System] sells a variety of unique products, and we really appreciate the effort they put into sharing elements of their design and manufacturing processes. This time, it’s details of the work that went into designing a luxury lamp shade that caught our eye.

Top: Finished lamp. Bottom: Partially-assembled.

The finished lamp shade is spherical, but is made entirely from flat-packed pieces of laser-cut wood that have been specifically designed to minimize distortion when assembled into a curved shape. The pieces themselves are reminiscent of puzzle cells; complex, interlocking cellular shapes found in many plants.

As usual, [Nervous System] applied a hefty dose of math and computational design to arrive at a solution. Each unique panel of the lamp is the result of a process that in part implements a technique called variation surface cutting for the shape of the pieces. They also provide a couple of nifty animations that illustrate generating both the piece boundaries as well as the hole patterns in each of the 18 unique pieces that make up each lamp.

As for making the pieces themselves, they are laser-cut from wood veneer, and assembly by the end user takes an hour or two. Watch a video overview, embedded just below under the page break.

We’re glad [Nervous System] takes the time to share details like this, just like the time they figured out the very best type of wood for laser-cutting their unique puzzles and didn’t keep it to themselves.

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Light projected through prisms on to laser-cut letters submerged in water.

YOU Are A Projection Of Your Influences

Who are you? No, who are you really? You’re an amalgamation of influences from your family, your friends, the media, and the parasocial relationships you have with fictional characters. It’s okay; we all are. It can’t be helped that there’s a lot of it about.

[Kim Pimmel]’s YOU examines this question of identity in the form of  projected typography. YOU are solidly laser-cut at birth, but then come the influences — the water of everyday life that surrounds you, the lights that mask your dread or lay you bare, and the prisms of circumstance that twist the light into brilliant patterns that burn memories into your brain.

In this case, the light comes from a hacked camping headlamp that was past its prime. [Kim] laser-cut the letters from acrylic and submerged them in water, which can be manipulated to enhance the effect and mimic the turmoil of life. For added effect, [Kim] held prisms in the light’s path to refract it and cause the patterns to dance. Be sure to check it out after the break, and don’t forget to turn on the sound so you can hear [Kim]’s original composition.

Want to see more trippy typography? Check out this vector art that started as Perlin noise.

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The X-PC, A Stylish Re-Imagining Of An Old Laptop

There’s one certainty wherever schoolchildren come into contact with computers: the hardware will inevitably emerge worse for the encounter. The school laptops managed by [Neil Lambert] certainly suffered, losing keys and power supplies aplenty. Faced with a pile of broken machines, he came up with the X-PC, a stylish all-in-one desktop computer built around the innards of a laptop.

Inside a modern laptop there is surprisingly little in the way of parts, now that removable media drives are largely a thing of the past and once the battery has been removed from the equation. When the keyboard and trackpad are subtracted and replaced with USB equivalents the inner workings are reduced to a relatively compact motherboard and hard drive alongside the screen.

The screen is encased in a lasercut frame that also mounts the motherboard. It includes a lasercut cover that folds over the top in a living hinge to create an A-frame case that also holds the power supply. As an extra bonus the centre of the A provides handy storage for a keyboard.

Most of us will have encountered enough older laptops with broken parts to recognise the value in this build, seeing how it can transform junk into a useful machine. This certainly isn’t the first time we’ve seen someone try a similar build.

Cleaner Laser Cutting With A 3D-Printed Nozzle

[Nervous System] does a lot of laser cutting, and [Jesse] shared a fascinating experimental improvement to their laser cutter that consists of a 3D-printed nozzle for cleaner cuts. You can see the results for yourself above, where the difference between the two cuts is striking.

[Jesse]’s modification doesn’t affect the laser beam itself; it is an improvement on the air assist, which is the name for a constant stream of air that blows away smoke and debris as the laser burns and vaporizes material. An efficient air assist is one of the keys to getting nice clean laser cuts, but [Jesse] points out that a good quality air assist isn’t just about how hard the air blows, it’s also about how smoothly it does so. A turbulent air assist can make scorch marks worse, not better.

3D-printed nozzle to promote laminar air flow on the left, stock nozzle on the right.

As an experiment to improve the quality of the air flowing out the laser nozzle, [Jesse] researched ways to avoid turbulence by creating laminar flow. Laminar flow is the quality of a liquid having layers flowing past one another with little or no mixing. One way to do this is to force liquid through individual, parallel channels as it progresses towards a sharply-defined exit nozzle. While [Jesse] found no reference designs of laminar flow nozzles for air assists, there were definitely resources on making laminar flow nozzles for water. It turns out that interest in such a nozzle exists mainly as a means of modifying Lonnie Johnson’s brilliant invention, the Super Soaker.

Working from such a design, [Jesse] created a custom nozzle to help promote laminar flow. Sadly, a laser cutter head carries design constraints that make some compromises unavoidable; one is limited space, and another is the need to keep the laser’s path unobstructed. Still, after 3D printing it in rigid heat-resistant resin, [Jesse] found a dramatic improvement in the feel of the air exiting the nozzle. Some test cuts confirmed a difference in performance, which results in a noticeably cleaner kerf without scorching around the edges.

One of the things [Nervous System] does is make their own custom puzzles, so any improvement to laser cutting helps reliability and quality. When production is involved, just about everything matters; a lesson [Nervous System] shared when they discussed making the best plywood for creating their puzzles.

Building One Test Fixture To Rule Them All

Test and programming fixtures are great time-savers for anyone who needs to deal with more than a handful of PCBs. Instead of plugging in connectors (or awkwardly holding probe tips or wires) to program some firmware or run tests, one simply pops a PCB into a custom fixture with one hand, and sips a margarita with the other while a program decides whether everything is as it should be. Test fixtures tend to be custom-made for specific board layouts, meaning one tester is needed per board or device type, but this work is easily justified by the huge time savings they offer.

An inserted PCB sits atop the thick acrylic piece, with pogo pins making contact from below. Generous space on the left and right make sure there is clearance for any mounted components. Visible near the bottom of the green board are output LEDs, and two touch-sensitive pads.

But the fine folks at Sparkfun’s quality control department figured they could save even more time by exploiting common design features across different boards, and shared details about designing a single test fixture flexible enough to handle multiple board types and designs.

The test unit looks like pretty familiar stuff at first glance: some hardware responsible for running the test program, laser-cut acrylic jig to hold a test PCB in a consistent position, spring-loaded pogo pins to make temporary electrical connections, and LEDs to clearly indicate PASS and FAIL states. The clever part is the way the fixture is designed to accommodate multiple board designs, and how it uses several 74LVC4066 quad bilateral switch ICs to take care of switching which pogo pins are connected and to where.

As mentioned, to be compatible with multiple boards there must be common design elements to exploit. In Sparkfun’s case, the through-hole connections on their breakout boards are all in a row with standard 0.1″ spacing. By using the aforementioned pogo pins and 4066 ICs, different pinouts can be accommodated and multiple board types can be used without any need to swap to different test hardware.

Test and programming fixtures, being one-offs, tend to have a lot of space for creativity and often show clever design or re-purposing of parts. Our own [Bob Baddeley] explains all about them here.

A Foam Core Stand Against Tablet Design

We hadn’t considered how challenging it might be to try drawing long-term on a tablet, and it sounds as though Apple didn’t, either. According to [Eric Strebel], who normally designs products for other people, there are many problems to solve. The camera area creates a bump on an otherwise flat backside, so it wobbles on the table. It’s thick. It’s too easy to run your stylus off the side.

Yes there are tablet holders out there, even a few with cup holders, but almost none of them have a kickstand for holding the thing vertically. If you want something done right, you have to do it yourself. And so [Eric] designed his ideal stand to solve all of these problems (video, embedded below). It’s mostly made of laser-cut foam core board, with some layers of poster board added to make the bezel totally flush with the tablet.

[Eric] can snap the tablet in place and use it flat, or fold back the upper half into a stand. It even works well over on the couch, or sitting up in bed. We particularly like the window gasket feet and all the versions of his hinges, which start with strips of cheesecloth and end in grosgrain ribbon. [Eric]’s approach to design always reminds us to keep an open mind about materials and methods. If you try using what you already have, the results may surprise you. Check out the build video after the break.

Maybe you don’t need or want a tablet stand. How about a foam core spray booth?

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