Schlieren On A Stick

August 25, 2020 by Bryan Cockfield 10 Comments

Schlieren imaging is a technique for viewing the density of transparent fluids using a camera and some clever optical setups. Density of a fluid like air might change based on the composition of the air itself with various gasses, or it may vary as a result of a sound or pressure wave. It might sound like you would need a complicated and/or expensive setup in order to view such things, but with a few common things you can have your own Schlieren setup as [elad] demonstrates.

His setup relies on a cell phone, attached to a selfie stick, with a spherical mirror at the other end. The selfie stick makes adjusting the distance from the camera to the mirror easy, as a specific distance from the camera is required as a function of focal length. For cell phone cameras, it’s best to find this distance through experimentation using a small LED as the point source. Once it’s calibrated and working, a circular field of view is displayed on the phone which allows the viewer to see any change in density in front of the mirror.

The only downside of this build that [elad] notes is that the selfie stick isn’t stiff enough to prevent the image from shaking around a little bit, but all things considered this is an excellent project that shows a neat and useful trick in the photography/instrumentation world that could be useful for a lot of other projects. We’ve only seen Schlieren imaging once before and it used a slightly different method of viewing the changing densities.

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Intro To Docker: Why And How To Use Containers On Any System

September 5, 2018 by Ben James 72 Comments

If you have your ear even slightly to the ground of the software community, you’ll have heard of Docker. Having recently enjoyed a tremendous rise in popularity, it continues to attract users at a rapid pace, including many global firms whose infrastructure depends on it. Part of Docker’s rise to fame can be attributed to its users becoming instant fans with evangelical tendencies.

But what’s behind the popularity, and how does it work? Let’s go through a conceptual introduction and then explore Docker with a bit of hands-on playing around.

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Old Rabbit Ears Optimized For Weather Satellite Downlink

July 10, 2017 by Dan Maloney 10 Comments

Communicating with a satellite seems like something that should take a lot of equipment. A fancy antenna and racks full of receivers, filters, and amplifiers would seem to be the entry-level suite of gear. But listening to a weather satellite with an old pair of rabbit ears and an SDR dongle? That’s a thing too.

There was a time when a pair of rabbit ears accompanied every new TV. Those days are gone, but [Thomas Cholakov (N1SPY)] managed to find one of the old TV dipoles in his garage, complete with 300-ohm twinlead and spade connectors. He put it to work listening to a NOAA weather satellite on 137 MHz by configuring it in a horizontal V-dipole arrangement. The antenna legs are spread about 120° apart and adjusted to about 20.5 inches (52 cm) length each. The length makes the antenna resonant at the right frequency, the vee shape makes the radiation pattern nearly circular, and the horizontal polarization excludes signals from the nearby FM broadcast band and directs the pattern skyward. [Thomas] doesn’t mention how he matched the antenna’s impedance to the SDR, but there appears to be some sort of balun in the video below. The satellite signal is decoded and displayed in real time with surprisingly good results.

Itching to listen to satellites but don’t have any rabbit ears? No problem — just go find a cooking pot and get to it.

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Fake Your ID Photos – The 3D Way

June 24, 2017 by Lewin Day 43 Comments

Photographs for identification purposes have strict requirements. Lighting, expression, and framing are all controlled to enable authorities to quickly and effectively use them to identify individuals reliably. But what if you created an entirely fake photograph from scratch? That’s exactly what [Raphael Fabre] set out to do.

With today’s 3D modelling tools, human faces can be created in extreme detail. Using these, [Raphael] set out to create a 3D model of himself, which was then used to render images simulating a passport photograph. Not content to end the project there, [Raphael] put his digital doppelgänger to the test – applying for a French identification card. He succeeded.

While the technology to create and render high-quality human faces has existed for a while, it’s impressive that [Raphael]’s work passed for genuine human. Obviously there’s something to be said for the likelihood of an overworked civil servant catching this sort of ruse, but the simple fact is, the images made it through the process, and [Raphael] has his ID. Theoretically, this leaves open the possibility of creating entirely fictitious characters and registering them as real citizens with the state, for all manner of nefarious purposes. If you do this, particularly on a grand scale, be sure to submit it to the tip line.

We’ve seen other concerning ID hacks before, such as this attempt at hacking RFIDs in Passport Cards.

File Format Posters

April 7, 2017 by Lewin Day 28 Comments

It’s not uncommon for hackers to have a particular delectation for unusual interior decoration. Maybe it’s a Nixie tube clock, or a vacuum fluorescent display reading out the latest tweets from a favorite chatbot. If this sounds like your living room already, perhaps you’d like some of these file format posters to adorn your walls.

The collection of images includes all kinds of formats — GIF, ZIP and WAV are all represented, but it even gets into some real esoterica — DOLphin format executables are here if you’re a total GameCube fanatic. Each poster breaks down the format into parts, such as the header, metadata and descriptor sections, and come in a variety of formats themselves — most available in SVG, PDF and PNG.

If we’re totally honest, these aren’t all designed for hanging on your wall as-is — we’d consider putting some work into to optimize the color palettes and layouts before putting these to print. But regardless, they’re an excellent visual representation of data structures that you might find particularly useful if you need to do some reverse engineering down the track.

If you still have wall space available after seeing this, here’s the electronic reference poster that should fill it.

[Thanks to JD for the tip!]

Hacklet 97 – Camera Projects

February 26, 2016 by Adam Fabio 9 Comments

We last covered camera projects way back in Hacklet #11. A ton of camera projects have been added to Hackaday.io since then. While the rest of the world is taking selfies, hackers, makers, and engineers have been coming up with new ways to hack their image capture devices. This week on the Hacklet, we’re taking a look at some of the best camera projects on Hackaday.io!

First up is [aleksey.grishchenko] with PiXel camera. PiXel is a camera and a live video display all in one, We wouldn’t exactly call it high-definition though! A Raspberry Pi uses its camera module to capture images of the world. [Aleksey] then processes those images and displays them on a 32 x 32 RGB LED matrix. This matrix is the same kind of tile used in large outdoor LED signs. The result is a surreal low resolution view of the world. Since the Pi, batteries, and camera all hide behind the LED matrix, there is an unobstructed view of the world around you. [Aleksey] used [Henner Zeller’s] matrix library to make this hack happen.

Next up is [Esben Rossel] with Linear CCD module. [Esben] is building a Raman spectrometer, much like 2014 Hackaday Prize finalist [fl@C@] with his own ramanPi. The heart of a spectrometer is the linear image capture device. Both of these projects use the same TCD1304 linear CCD. Linear Charge Coupled Devices (CCDs) are the same type of device used in flatbed document scanners. The output of the CCD is analog, so an ADC must be used to capture the data. [Esben] is using an STM32F401RE on a Nucleo board as the control logic. The ST’s internal ADC converts the analog signal to digital. From there, it’s time to process all the spectra.

[Chiprobot] brings the classic Wii remote camera to the internet of things with
ESP8266 meets Wii Mote Camera. The Wii remote uses a camera which doesn’t output images, instead it plots the location of up to four IR LEDs. Normally these LEDs are located in the poorly named sensor bar that is sold with the Wii. Hackers have been using these cameras in projects for years now. [Chiprobot] paired his camera with the modern classic ESP8266 WiFi module. The ‘8266 is programmed to read data from the camera’s I2C bus. It then sends the data as an SVG request to the W3C website. W3C returns a formatted image based on those coordinates. The resulting image is a picture of the IR LEDs seen by the camera. Kind of like sending your negatives out to be developed.

Finally, we have [GuyisIT] with Raspberry Pi Photobooth. Photo booths are all the rage these days. First it was weddings, but now it seems like every kids party has one. [GuyisIT] didn’t rent a booth for his daughter’s birthday, he built one using his Raspberry Pi and Pi camera. The project is written in python, based upon [John Croucher’s] code. When the kids press a button, the Pi Snaps a series of pictures. The tiny Linux computer then joins and rotates the images while adding in some superhero themed graphics. Finally the Pi prints the image on to a photo printer. The biggest problem with this hack is re-triggering. The kids loved it so much, they kept pressing the big red button!

If you want to see more camera projects, check out our updated camera projects list! If I missed your project, don’t be shy! Just drop me a message on Hackaday.io. That’s it for this week’s Hacklet. As always, see you next week. Same hack time, same hack channel, bringing you the best of Hackaday.io!

Stegosploit: Owned By A JPG

November 6, 2015 by Elliot Williams 34 Comments

We’re primarily hardware hackers, but every once in a while we see a software hack that really tickles our fancy. One such hack is Stegosploit, by [Saumil Shah]. Stegosploit isn’t really an exploit, so much as it’s a means of delivering exploits to browsers by hiding them in pictures. Why? Because nobody expects a picture to contain executable code.

[Saumil] starts off by packing the real exploit code into an image. He demonstrates that you can do this directly, by encoding characters of the code in the color values of the pixels. But that would look strange, so instead the code is delivered steganographically by spreading the bits of the characters that represent the code among the least-significant bits in either a JPG or PNG image.

OK, so the exploit code is hidden in the picture. Reading it out is actually simple: the HTML canvas element has a built-in getImageData() method that reads the (numeric) value of a given pixel. A little bit of JavaScript later, and you’ve reconstructed your code from the image. This is sneaky because there’s exploit code that’s now runnable in your browser, but your anti-virus software won’t see it because it wasn’t ever written out — it was in the image and reconstructed on the fly by innocuous-looking “normal” JavaScript.

And here’s the coup de grâce. By packing HTML and JavaScript into the header data of the image file, you can end up with a valid image (JPG or PNG) file that will nonetheless be interpreted as HTML by a browser. The simplest way to do this is send your file myPic.JPG from the webserver with a Content-Type: text/html HTTP header. Even though it’s a totally valid image file, with an image file extension, a browser will treat it as HTML, render the page and run the script it finds within.

The end result of this is a single image that the browser thinks is HTML with JavaScript inside it, which displays the image in question and at the same time unpacks the exploit code that’s hidden in the shadows of the image and runs that as well. You’re owned by a single image file! And everything looks normal.

We like this because it combines two sweet tricks in one hack: steganography to deliver the exploit code, and “polyglot” files that can be read two ways, depending on which application is doing the reading. A quick tag-search of Hackaday will dig up a lot on steganography here, but polyglot files are a relatively new hack.

[Ange Ablertini] is the undisputed master of packing one file type inside another, so if you want to get into the nitty-gritty of [Ange]’s style of “polyglot” file types, watch his talk on “Funky File Formats” (YouTube). You’ll never look at a ZIP file the same again.

Sweet hack, right? Who says the hardware guys get to have all the fun?