A pair of PCBs with OLED character displays, showing a simple encryption program

The CryptMaster 2001 Provides Basic Lessons In Cryptography

February 13, 2023 by Robin Kearey 6 Comments

Sending secret messages to your friends is fun, but today it’s so simple that you don’t even notice it anymore: practically any serious messaging system features encryption of some sort. To teach his kids about cryptography, [Michal Zalewski] therefore decided to bring the topic to life by building a handheld encryption system, called the CryptMaster 2001.

The system consists of an identical pair of hand-held devices built on prototype PCBs. A standard 16×2 character OLED display is used as an output device, which generates the ciphertext in real time as the plaintext is entered character by character through a rotary encoder. An ATmega328P manages the input and output routines and performs the encryption.

For ease of use, [Michal] wanted to use a reciprocal cipher, meaning one that uses the same operation for encryption and decryption. Trivial ciphers like ROT13 would be a bit too easy to crack, so he devised a slightly more complex system where each character in the input is encoded using a separate rearranged alphabet – a basic polyalphabetic substitution cipher.

[Michal]’s kids apparently had some good fun with the CryptMaster 2001, until his eldest son managed to reverse-engineer the encryption method, enabling him to decode messages without having access to one of the devices. This made the project a pretty decent lesson about the limits of basic cryptography: simply swapping letters doesn’t present a real challenge to anyone. Luckily, much more secure methods are available, even if you’re only using pen and paper.

Your Next Wearable May Not Need Electricity

November 17, 2017 by Kristina Panos 9 Comments

What if you could unlock a door with your shirtsleeve, or code a secret message into your tie? This could soon be a thing, because researchers at the University of Washington have created a fabric that can store data without any electronics whatsoever. The fabric can be washed, dried, and even ironed without losing data. Oh, and it’s way cheaper than RFID.

By harnessing the ferromagnetic properties of conductive thread, [Justin Chen] and [Shyam Gollakota] have proved the ability to store bit strings and 2D images through magnetization. The team used an embroidery machine to lay down thread in dense strips and patches, and then coded in ones and zeros by rubbing the threads with N and S neodymium magnets.

They didn’t use anything special, either, just this conductive thread, some magnets, and a Nexus 5 to read the data. Any phone with a magnetometer (so, most of them) could decode this type of binary data. The threads stay reliably magnetized for about a week and then begin to weaken. However, their tests proved that the threads can be re-magnetized over and over.

The team also created 2D images with magnets on a 9-patch made of conductive fabric. The images can be decoded piecemeal by a single magnetometer, or all at once by an array of them. Finally, the team made a glove with a magnetized patch of thread on the fingertip. They were able to get the phone to recognize six unique gestures with 90% accuracy, even with the phone tucked away in a pocket. See it in action in their demo video after the break.

Magnetic memory is certainly not a new concept. But for the wearable technology frontier, it’s a novel one.

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Trick Google Used Hides Secret Messages On LCD Screens

July 15, 2015 by Adam Fabio 37 Comments

[Travis] didn’t get picked to go to Google I/O this year, but he did have some I/O inspired fun after the fact. His friends who did go told him about specially modified LCD screens Google had scattered around the event. The screens showed normal show information when viewed with the naked eye. When viewed through a special transparent badge included with the I/O swag though, a URL for Google’s scavenger hunt would magically appear. [Travis] was intrigued by the effect, and became hell-bent on reproducing it himself.

[Travis] figured out the transparent badge was actually a polarizing filter. Every standard LCD has two of them, usually bonded to the glass of the LCD itself. If you remove the filters from a LCD, you’ll get a prime view of the backlight – unless you’re wearing polarizing glasses of course. Google’s monitors didn’t have that effect though. They showed a full color display, with a second full color hidden display only visible through the polarizer. [Travis] is intelligent and experienced, so it only took a bit of three-dimensional thinking for him to figure out Google’s trick. There are actually two LCDs used in the display. The first is a standard LCD with backlight. The trick is to strip the polarizing film off a second LCD and place it in front of the first. The second LCD will be invisible to anyone – without the polarizer.

[Travis] quickly set about replicating the display using several obsolete VGA LCDs. He quickly found that the hard part was peeling the polarizing plastic from the thin glass LCD sandwich. Several LCDs gave up their lives in the effort, but in the end [Travis] was successful. He made everything fit in one case by using a thin LED backlight in a case designed for a monitor with a Cold Cathode Fluorescent Lamp (CCFL). The result looks exactly like a standard LCD – that is, until viewed through a polarizing filter. Click past the break to see the hidden message LCD in action!

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