Unlocking A Locked-Down Inverter

November 25, 2022 by Jenny List 21 Comments

There was a time when a mains inverter was a heavy, expensive, and not particularly powerful item, but thanks to switch-mode technology we are now spoiled for choice. Most inverters still work with 12 V or 24 V supplies though, so when [Chris Jones] was looking for one to run from 36 V batteries, he found a limited supply. Sadly the Greenworks model he ended up with was affordable, but locked to a particular battery by means of a serial line between battery and inverter. Buy the special battery? No, he did what any hacker would do, and modified the inverter to do without it.

Tracing the serial link led to a mystery chip, probably a microcontroller but without available data. It in turn had a line to an 8051 derivative that seemed to be the brains of the operation. Acting on a hunch he pulled down the line with a resistor, and as if by magic, a working inverter appeared.

As you might expect, here at Hackaday we abhor such tricks by manufacturers, and thus any moves to circumvent them are to be applauded. It would be extremely interesting were anyone to have the Greenworks battery to subject to some reverse engineering of the profile.

Meanwhile if this is a little complex for you, there is a much simpler way to make a rough and ready inverter.

Reverse Engineering “The Seven Words (and More) You Can’t Say On TV”

November 21, 2022 by Dan Maloney 24 Comments

For as visionary as he was, [George Carlin] vastly underestimated the situation with his classic “Seven Words You Can’t Say on TV” bit. At least judging by [Ben Eater]’s reverse engineering of the “TVGuardian Foul Language Filter” device, it seems like the actual number is at least 20 times that.

To begin at the beginning, a couple of weeks ago [Alec] over at everyone’s favorite nerd hangout Technology Connections did a video on the TVGuardian, a device that attempted to clean up the language of live TV and recorded programming. Go watch that video for the details, but for a brief summary, TVGuardian worked by scanning the closed caption text for naughty words and phrases, muted the audio when something suggestive was found in a lookup table, and inserted a closed caption substitute for the offensive content. In his video, [Alec] pined for a way to look at the list of verboten words, and [Ben] accepted the challenge.

The naughty word list ended up living on a 93LC86 serial EEPROM, which [Ben] removed from his TVGuardian for further exploration. Rather than just plug it into a programmer and dumping the contents, he decided to roll his own decoder with an Arduino, because that’s more fun. And can we just point out our ongoing amazement that [Ben] is able to make watching someone else code interesting?

The resulting NSFW word list is titillating, of course, and the video would be plenty satisfying if that’s where it ended. But [Ben] went further and figured out how the list is organized, how the dirty-to-clean substitutions are made, and even how certain words are whitelisted. That last bit resulted in the revelation that Hollywood legend [Dick Van Dyke] gets a special whitelisting, lest his name becomes sanitized to a hilarious [Jerk Van Gay].

Hats off to [Alec] for inspiring [Ben]’s fascinating reverse engineering effort here.

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Scramblepad Teardown Reveals Complicated, Expensive Innards

November 18, 2022 by Donald Papp 28 Comments

What’s a Scramblepad? It’s a type of number pad in which the numbers aren’t in fixed locations, and can only be seen from a narrow viewing angle. Every time the pad is activated, the buttons have different numbers. That way, a constant numerical code isn’t telegraphed by either button wear, or finger positions when punching it in. [Glen Akins] got his hands on one last year and figured out how to interface to it, and shared loads of nice photos and details about just how complicated this device was on the inside.

Just one of the many layers inside the Scramblepad.

Patented in 1982 and used for access control, a Scramblepad aimed to avoid the risk of someone inferring a code by watching a user punch it in, while also preventing information leakage via wear and tear on the keys themselves. They were designed to solve some specific issues, but as [Glen] points out, there are many good reasons they aren’t used today. Not only is their accessibility poor (they only worked at a certain height and viewing angle, and aren’t accessible to sight-impaired folks) but on top of that they are complex, expensive, and not vandal-proof.

[Glen]’s Scramblepad might be obsolete, but with its black build, sharp lines, and red LED 7-segment displays it has an undeniable style. It also includes an RFID reader, allowing it to act as a kind of two-factor access control.

On the inside, the reader is a hefty piece of hardware with multiple layers of PCBs and antennas. Despite all the electronics crammed into the Scramblepad, all by itself it doesn’t do much. A central controller is what actually controls door access, and the pad communicates to this board via an unencrypted, proprietary protocol. [Glen] went through the work of decoding this, and designed a simplified board that he plans to use for his own door access controller.

In the meantime, it’s a great peek inside a neat piece of hardware. You can see [Glen]’s Scramblepad in action in the short video embedded below.

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Reverse Engineering Reveals EV Charger Has A Sense Of Security

November 16, 2022 by Dan Maloney 11 Comments

As more and more electric vehicles penetrate the market, there’s going to have to be a proportional rise in the number of charging stations that are built into parking garages, apartment complexes, and even private homes. And the more that happens, the more chargers we’re going to start seeing where security is at best an afterthought in their design.

But as this EV charger teardown and reverse engineering shows, it doesn’t necessarily have to be that way. The charger is a Zaptec Pro station that can do up to 22 kW, and the analysis was done by [Harrison Sand] and [Andreas Claesson]. These are just the kinds of chargers that will likely be widely installed over the next decade, and there’s surprisingly little to them. [Harrison] and [Andreas] found a pair of PCBs, one for the power electronics and one for the control circuits. The latter supports a number of connectivity options, like 4G, WiFi, and Bluetooth, plus some RFID and powerline communications. There are two microcontrollers, a PIC and an ARM Cortex-A7.

Despite the ARM chip, the board seemed to lack an obvious JTAG port, and while some unpopulated pads did end up having a UART line, there was no shell access possible. An on-board micro SD card slot seemed an obvious target for attack, and some of the Linux images they tried yielded at least a partial boot-up, but without knowing the specific hardware configuration on the board, that’s just shooting in the dark. That’s when the NAND flash chip was popped off the board to dump the firmware, which allowed them to extract the devicetree and build a custom bootloader to finally own root.

The article has a lot of fascinating details on the exploit and what they discovered after getting in, like the fact that even if you had the factory-set Bluetooth PIN, you wouldn’t be able to get free charging. So overall, a pretty good security setup, even if they were able to get in by dumping the firmware. This all reminds us a little of the smart meter reverse engineering our friend [Hash] has been doing, in terms of both methodology and results.

Thanks to [Thinkerer] for the tip.

“Reversing Shorts” Demystify Phone Security

October 24, 2022 by Elliot Williams 3 Comments

Ever wonder what makes a cellphone’s operating system secure, or what that app you just installed is saying about you behind your back? In a brand new video series, [Jiska] gives us a peek into different topics in smartphone software reverse engineering.

For instance, her latest video, embedded below takes us through some steps to poke at Apple’s RTKit OS, which is the realtime OS that runs inside most of their peripheral devices, including AirPods, but also on their bigger devices too. We don’t know much about RTKit OS, but [Jiska]’s trick in this video is to get a foothold by looking through two different RTKit OS versions and noting which symbols are common — these are probably OS function names. Now you’ve got something to look for.

Each of the videos is short, to the point, and contains nice tips for perhaps the intermediate-to-advanced reverser who is looking to get into phones. Heck, even if you’re not, her demonstrations of the Frida dynamic tracing tool are worth your time.

And if you want a longer introduction into the internals of cellphones, we heartily recommend her talk, “All Wireless Stacks Are Broken“.

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When [Elon] Says No, Just Reverse Engineer The Starlink Signal

October 22, 2022 by Dan Maloney 37 Comments

We all know that it’s sometimes better to beg forgiveness than ask permission to do something, and we’ll venture a guess that more than a few of us have taken that advice to heart on occasion. But [Todd Humphreys] got the order of operations a bit mixed up with his attempt to leverage the Starlink network as a backup to the Global Positioning System, and ended up doing some interesting reverse engineering work as a result.

The story goes that [Todd] and his team at the University of Texas Austin’s Radionavigation Lab, on behalf of their sponsors in the US Army, approached Starlink about cooperating on a project to make their low-Earth orbit constellation provide position, navigation, and timing capabilities. Although initially interested in the project, Starlink honcho [Elon Musk] put the brakes on things, leaving [Todd]’s team high and dry. Not to be dissuaded, they bought a Starlink user terminal, built what amounts to a small radiotelescope — although we’ve seen something similar done with just an RTL-SDR — and proceeded to reverse-engineer the structure of Starlink’s Ku-band downlink signal. The paper (PDF link) on their findings is densely packed with details, such as the fact that Starlink uses an orthogonal frequency-division multiplexing (OFDM) scheme.

It’s important to note that their goal was not to break encryption or sniff in on user data; rather, they wanted access to the synchronization and timing signals embedded in the Starlink data structures. By using this data along with the publically available ephemera for each satellite, it’s possible to quickly calculate the exact distance to multiple satellites and determine the receiver’s location to within 30 meters. It’s not as good as some GPS-Starlink hacks we’ve seen, but it’s still pretty good in a pinch. Besides, the reverse engineering work here is well worth a read.

Thanks to [Adrian] for the tip!

Hunt Down NFC Signals With This NFC Multi Tool

October 17, 2022 by Abe Connelly 6 Comments

NFC hacking can be a daunting task with many specialized tools, a proliferation of protocols, and a multitude of different devices. [ElectronicCats] has done a lot of work to try to make this investigation accessible by creating an open-source, hardware-certified NFC tool called the HunterCatNFC that can read and emulate a multitude of NFC devices.

The HunterCatNFC device is meant to be portable and self contained, with LED indicator lights that can give information about the various modes, and feedback about what data is being received. At its core, the HunterCatNFC has an NXP PN7150 NFC controller chip to handle the NFC communication. The main processing controller is a Microchip SAMD21 which also provides USB functionality, and the whole device is powered by a 3.7V 150mAh Li-ion battery.

The HunterCatNFC has three main modes, ’emulation’, ‘read/write’ and ‘peer-to-peer’. Emulation mode allows the HunterCatNFC to mimic the functionality of a passive NFC device, only responding when an NFC reader issues a request. The read/write mode allows it to emulate an NFC reader or writer, with the ability to communicate with nearby passive NFC devices. The peer-to-peer mode gives the device the ability to have two way communication, for instance, between two HunterCatNFC devices.

We’ve covered NFC hacking before, including the Flipper Zero. The HunterCatNFC is a fine addition to the NFC hackers arsenal of tools with some very nice documentation to learn from. For those not wanting to send out their own boards to be printed and assembled, [ElectronicCats] has them for sale.

Video after the break!

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