Reverse Engineering

296 Articles

North Korean Karaoke Machine Teardown

May 19, 2023 by 9 Comments

Karaoke is a very popular pastime in Seoul — there are venues where you can sing on a stage, sing in rooms with your friends, and even sing solo in coin-operated karaoke booths on the bullet train. Apparently it is also popular in North Korea as well — [Martyn Williams] of the North Korea Tech blog reported on an interesting teardown by web hacker [Will Scott]. It is the Tianchi v700 machine, a Chinese product tailored for North Korean users, obtained online back in 2020.

Unlike the karaoke machines encountered by this author in South Korea, the v700 form factor is a 19.5-inch Android tablet with touch-screen and all the necessary interfaces you’d expect: external video, speakers, and microphone, as well as WiFi and Ethernet for content upgrade and online payment systems. Not surprisingly, the connectivity aspects of the machine are not used in the North Korean model, but with a large catalog of pre-loaded music, it’s perfectly usable as a stand-alone device.

[Will] dug into the innards of the machine and discovered it was powered by an Allwinner ARM processor (seemingly the H6 V200, a quad-core ARM Cortex-A53). He also found it uses a swappable external disk to hold the songs, but all the files were encrypted. You can read more details in the blog post linked above, but eventually he was successful in decoding the disk and accessing the material.

The V700 consults both “/proc/cpuinfo” to learn the CPU serial number of the device it is on, and a binary file associated with the device file system structure as part of its method for determining its AES (Advanced Encryption Standard) key. It then ignores all of these device-specific items, and reverts back to a static key “87654321” stored in the binary.

All the songs on the disk were posted up on the Internet Archive. Check them out if you’re curious what North Korean karaoke songs sound and look like. One video that caught our attention was about CNC machines (see the video linked below the break). [Martyn] has been covering technology issues related to North Korea since 2011. In 2016, he learned after the fact that his website had been banned by the South Korean authorities. Believing this was in error, he appealed the ban and eventually prevailed in the courts. We wrote about some of [Will]’s research on consumer computing technology back in 2017 if you’re interested in learning more.

Continue reading “North Korean Karaoke Machine Teardown” →

Reverse Engineering An Oil Burner Comms Board, With A Few Lucky Breaks

May 11, 2023 by 3 Comments

Here’s a question for you: How do you reverse engineer a circuit when you don’t even have it in hand? It’s an interesting problem, and it adds a level of difficulty to the already iffy proposition that reverse engineering generally presents. And yet, not only did [themole] find a way to replicate a comms board for his oil burner, he extended and enhanced the circuit for integration into his home automation network.

By way of backstory, [themole] has a wonky Buderus oil burner, which occasionally goes into safety mode and shuts down. With one too many cold showers as a result, he looked for ways to communicate with the burner controller. Luckily, Buderus sells just the thing — a serial port module that plugs into a spare slot in the controller. Unluckily, the board costs a bundle, and that’s even if you can find it. So armed with nothing but photos of the front and back of the board, the finding of which was a true stroke of luck, he set about figuring out the circuit.

With only a dozen components or so and a couple of connectors, the OEM board gave up its secrets pretty easily; it’s really just a level shifter to make the boiler talk RS-232. But that’s a little passé these days, and [the78mole] was more interested in a WiFi connection. So his version of the card includes an ESP32 module, which handles wireless duties as well as the logic needed to talk to the burner using the Buderus proprietary protocol. The module plugs right into the burner controller and connects it to ESPHome, so no more cold showers for [themole].

We thought this one was pretty cool, especially the way [themole] used the online photos of the board to not only trace the circuit but to get accurate — mostly — measurements of the board using an online measuring tool. That’s a tip we’ll keep in our back pocket.

Thanks to [Jieffe] for the tip.

A white, house-shaped clock with the words "TEMPUS NECTIT" written in faux Roman script in black on a strip of silver at the base of the "roof." a white power cord extends from the left of the enclosure, and the center of the clock is a 22 pin knitting machine wheel with one pin covered in silver metalic. A white plastic peg extends from the bottom right of the enclosure to hold the feedstock yarn.

Tempus Nectit, A DIY Knitting Clock With Instructions

April 5, 2023 by 1 Comment

We’re no strangers to unusual clocks here at Hackaday, and some of our favorites make time a little more tangible like [Kyle Rankin]’s knitting clock.

Inspired by our coverage of [Siren Elise Wilhelmsen]’s knitting clock, [Rankin] decided to build one of his own. Since details on the build from the original artist were sparse, he had to reverse engineer how the device worked. He identified that a knitting clock is essentially a knitting machine with a stepper motor replacing the hand crank.

Using a Raspberry Pi with an Adafruit motor hat connected to a stepper motor and a 3D printed motor adapter, [Rankin] was able to drive the knitting machine to do a complete round of knitting every twelve hours. By marking one of the knitting pegs as an hour hand, the clock works as a traditional clock in addition to its year-long knitting task. [Rankin] says he still has some fine tuning to work on, but that he’s happy to have had the chance to combine so many of his interests into a single project.

If you’re looking for more knitting hacks, check out this knitted keyboard instrument or a knitted circuit board.

Continue reading “Tempus Nectit, A DIY Knitting Clock With Instructions” →

Debugging And Analyzing Real-Mode 16-Bit X86 Code With Fresh Bread

March 28, 2023 by 7 Comments

Running a debugger like gdb with real-mode 16-bit code on the x86 platform is not the easiest thing to do, but incredibly useful when it comes to analyzing BIOS firmware and DOS software. Although it’s possible to analyze a BIOS image after running it through a disassembler, there is a lot that can only be done when the software is running on the real hardware. This is where [Davidson Francis] decided that some BREAD would be useful, as in BIOS Reverse Engineering & Advanced Debugging.

What BREAD does is provide some injectable code that with e.g. a BIOS replaces the normal boot logo with the debugger stub. This stub communicates with a bridge via the serial port, with the gdb client connecting to this bridge. Since DOS programs are also often 16-bit real-mode, these can be similarly modified to provide light-weight in-situ debugging and analysis. We imagine that this software can be very useful both for software archaeology and embedded purposes.

Thanks to [Rodrigo Laneth] for the tip.

Creating A Game Boy ROM From Pictures

March 23, 2023 by 22 Comments

There are very few legal ways of obtaining ROM files for video games, and Nintendo’s lawyers are extremely keen on at least reminding you of the fact that you need to own the game cart before obtaining the ROM. With cart in hand, though, most will grab a cart reader to download the game files. While this is a tried-and-true method, for GameBoy games this extra piece of hardware isn’t strictly required. [Travis Goodspeed] is here to show us a method of obtaining ROM files from photographs of the game itself.

Bits can be manually edited to fix detection errors.

Of course, the chips inside the game cart will need to be decapped in order to obtain the pictures, and the pictures will need to be of high quality in order to grab the information. [Travis] is more than capable of this task in his home lab, but some work is still required after this step.

The individual bits in the Game Boy cartridges are created by metal vias on the chip, which are extremely small, but still visible under a microscope. He also has a CAD program that he developed to take this visual information and extract the data from it, which creates a ROM file that’s just as good as any obtained with a cart reader.

This might end up being slightly more work especially if you have to decap the chips and take the photographs yourself, but it’s nonetheless a clever way of obtaining ROM files due to this quirk of Game Boy technology. Encoding data into physical hardware like this is also an excellent way of ensuring that it doesn’t degrade over time. Here are some other methods for long-term data storage.

Screenshot of ImHex hex editor, with the MOC3 file structure being reverse-engineered inside of it

Live2D: Silently Subverting Threat Models

March 20, 2023 by 10 Comments

In online spaces, VTubers have been steadily growing in popularity in the past few years – they are entertainers using motion capture tech to animate a special-sauce 2D or 3D model, typically livestreaming it as their avatar to an audience. The tech in question is pretty fun, lively communities tend to form around the entertainers and artists involved, and there’s loads of room for creativity in the VTuber format; as for viewers, there’s a VTuber for anyone’s taste out there – what’s not to like? On the tech side of making everything work, most creators in the VTubing space currently go with a software suite from a company called Live2D – which is where today’s investigation comes in. Continue reading “Live2D: Silently Subverting Threat Models” →

Customizing The Start-Up Chime On A 1999 G3 IMac

March 19, 2023 by 3 Comments

The start-up chime on Macs is probably as recognizable as the default Nokia ringtone in this day and age. Yet much like a ringtone, so too one might want to change the start-up chime on a Mac. This is something which [Doug Brown] has done in the past already on a Power Mac G3 in 2012, which made him instantly an expert on the topic in the eyes of a reader who wanted to know how to change the chime on a 1999 iMac. While the firmware on both these systems is written in Forth, it did take a bit of sleuthing to figure out where the chime was hiding in the firmware image, and how to change it.

The target iMac is somewhat unique in that it has a G4 PPC CPU rather than the more common G3. The firmware is similar enough that it was a snap to simply search the newer iMac’s firmware for the signature of the chime sound data. This turned out to be the identical QuickTime IMA ADPCM format-encoded data, yet what was different was how this data was integrated into the firmware image. Key is finding the area in the firmware where not only the address of the chime data’s start is defined, but also its length. Finally, the checksums in the firmware image have to be updated so that it matches the patched data.

Reverse-engineering the checksum calculation in the Forth code turned out to be fairly straightforward, but getting the new firmware on the iMac turned out to be the biggest struggle, as [Doug] didn’t want to inflict running a manual firmware update onto this reader he was doing all this work for. This led [Doug] to do some more reverse-engineering using Ghidra to enable the use of the automatic updater like a regular firmware update.

In the end it all worked out great, and now another iMac no longer has the Mac chime on start-up.