Phone Hacks

184 Articles

Does Your Phone Need A RAM Drive?

October 19, 2020 by 73 Comments

Phones used to be phones. Then we got cordless phones which were part phone and part radio. Then we got cell phones. But with smartphones, we have a phone that is both a radio and a computer. Tiny battery operated computers are typically a bit anemic, but as technology marches forward, those tiny computers grew to the point that they outpace desktop machines from a few years ago. That means more and more phones are incorporating technology we used to reserve for desktop computers and servers. Case in point: Xiaomi now has a smartphone that sports a RAM drive. Is this really necessary?

While people like to say you can never be too rich or too thin, memory can never be too big or too fast. Unfortunately, that’s always been a zero-sum game. Fast memory tends to be lower-density while large capacity memory tends to be slower. The fastest common memory is static RAM, but that requires a lot of area on a chip per bit and also consumes a lot of power. That’s why most computers and devices use dynamic RAM for main storage. Since each bit is little more than a capacitor, the density is good and power requirements are reasonable. The downside? Internally, the memory needs a rewrite when read or periodically before the tiny capacitors discharge.

Although dynamic RAM density is high, flash memory still serves as the “disk drive” for most phones. It is dense, cheap, and — unlike RAM — holds data with no power. The downside is the interface to it is cumbersome and relatively slow despite new standards to improve throughput. There’s virtually no way the type of flash memory used in a typical phone will ever match the access speeds you can get with RAM.

So, are our phones held back by the speed of the flash? Are they calling out for a new paradigm that taps the speed of RAM whenever possible? Let’s unpack this issue.

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Linux Fu: The Linux Android Convergence

October 7, 2020 by 63 Comments

The Android phone that you carry in your pocket is basically a small computer running Linux. So why is it so hard to get to a usable Linux environment on your phone? If you could run Linux, you could turn your cell phone into an ultra-portable laptop replacement.

Of course, the obvious approach is just to root the phone and clean-slate install a Linux distribution on it. That’s pretty extreme and, honestly, you would probably lose a lot of phone function unless you go with a Linux-specific phone like the PinePhone. However, using an installer called AnLinux, along with a terminal program and a VNC client, you can get a workable setup without nuking your phone’s OS, or even having root access. Let’s see what we can do. Continue reading “Linux Fu: The Linux Android Convergence” →

AUTOVON: A Phone System Fit For The Military

September 9, 2020 by 55 Comments

It’s a common enough Hollywood trope that we’ve all probably seen it: the general, chest bespangled with medals and ribbons, gazes at a big screen swarming with the phosphor traces of incoming ICBMs, defeatedly picks up the phone and somberly intones, “Get me the president.” We’re left on the edge of our seats as we ponder what it must be like to have to deliver the bad news to the boss, knowing full well that his response will literally light the world on fire.

Scenes like that work because we suspect that real-life versions of it probably played out dozens of times during the Cold War, and likely once or twice since its official conclusion. Such scenes also play into our suspicion that military and political leaders have at their disposal technologies that are vastly superior to what’s available to consumers, chief among them being special communications networks that provide capabilities we could only have dreamed of back then.

As it turns out, the US military did indeed have different and better telephone capabilities during the Cold War than those enjoyed by their civilian counterparts. But as we shall see, the increased capabilities of the network that came to be known as AUTOVON didn’t come so much from better technology, but more from duplicating the existing public switched-telephone network and using good engineering principles, a lot of concrete, and a dash of paranoia to protect it.

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A Mobile Phone For The Pulse Dial Generation

July 29, 2020 by 7 Comments

One of the useful side effects of the ubiquitous availability of cellular network data modules is that they can be used to create custom mobile phones. It’s surprising in a way that we don’t see as many of these projects as we’d expect, but by way of redressing that deficiency we’re pleased to see the work of [Proton Gamer], who has taken a vintage rotary dial phone and upgraded it with an Arduino and GSM shield to make a very unexpected mobile phone project.

It’s not entirely certain from the write-up which manufacturer produced the donor phone or for which country’s network it was produced, but it seems typical of the type you might have found the world over in the 1960s. We’re given a breakdown of the various components and how to interface to them, the ringer for example is run using a motor driver board. There are comprehensive instructions for the conversion, though sadly they involve gutting the phone and removing the original hardware. The result can be seen in the video below the break, and the finished project makes a mobile phone call from the unlikeliest of hardware.

This certainly isn’t the first rotary dial mobile phone we’ve featured, including one based on a conference badge.

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BadPower Vulnerability In Fast Chargers Might Make Phones Halt And Catch Fire

July 22, 2020 by 21 Comments

A few days ago, Chinese researchers from technology giant Tencent released a paper outlining a firmware vulnerability in several types of fast charger power bricks (translated). The attack is known as BadPower, and it works by altering the default parameters in the firmware of fast chargers to deliver more power to devices than they can handle, which can cause them to overheat, melt, or catch fire.

The ancient and basic USB charging spec provides 0.5 A at 5 V, which is equal to 2.5 W. In theory, that’s all you’ll ever get from those types of chargers. But the newer generation of chargers are different. When you plug your phone into a fast charger, it negotiates a voltage and charging speed with your phone before passing it any power.

Fast chargers can push power at 20 V or more to speed up the charging process, depending on the charger and connected device. If the phone doesn’t do fast charging, it will default to the 5 V standard. Researchers claim the BadPower attack is capable of harming devices whether or not they include a fast charging feature. When a capable device is connected, the charger will still negotiate for 5V, but instead give 20V and wreak havoc.

In the demo after the break, one of the team uses a malicious device disguised as a phone to push the BadPower firmware change to a fast charger that’s hooked up to a voltmeter. Before the attack, the charger gives 5V. After the attack, it gives 5V for a few seconds before jumping up near 20V. Then they connect the now-dirty charger to two identical illuminated magnifying glasses. In one the chip lets the smoke monster out rather violently, and the chips of the other emit sparks.

The researchers tested 35 of the 200+ fast charging bricks currently on the market and found that 18 of them were vulnerable to BadPower, including 11 that can be exploited through the charging port itself. They believe the issue is fixable with a firmware update.

What is not available is enough information to verify this research, or a list of brands/models that are vulnerable. Researchers say the findings were submitted to the China National Vulnerability Database (CNVD) on March 27th, so the absence of this information may be a product of manufacturers needing more time to patch the vulnerability.

What do you think? We say halfway decent chargers shouldn’t be open to firmware attacks from the devices they are charging. And any halfway decent phone should have built-in electrical protection, right?

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Rotary Phone Takes You Around The World And Through Time – With Music

June 24, 2020 by 5 Comments

Purposely choosing obsoleted technology combines all the joy of simpler times with the comfort of knowing you’re not actually stuck with outdated (and oftentimes inferior) technology. The rotary phone is a great example here, and while rarely anyone would want to go back to the lenghty, error-prone way of dialing a number on it on an everyday basis, it can definitely add a certain charm to a project. [Caroline Buttet] thought so as well, and turned her grandma’s old rotary phone into a time-traveling, globe-trotting web radio.

The main idea is fairly simple: a Raspberry Pi connects via browser to a web radio site that plays music throughout the decades from places all over the world. [Caroline]’s implementation has a few nice twists added though. First of all, the phone of course, which doesn’t only house the Raspberry Pi, but serves both as actual listening device via handset speaker, and as input device to select the decade with the rotary dial. For a headless setup, she wrote a Chromium extension that maps key events to virtual clicks on the corresponding DOM element of the web site — like the ones that change the decade — and a Python script that turns the rotary dial pulses into those key events.

However, the phone is only half the story here, and the country selection is just as fascinating — which involves an actual world map. An audio connector is attached to each selectable country and connected to an Arduino. If the matching jack is plugged into it, the Arduino informs the Raspberry Pi via serial line about the new selection, and the same Chromium extension then triggers the country change in the underlying web site. You can check all the code in the project’s GitHub repository, and watch a demo and brief explanation in the videos after the break.

Sure, listening radio through a telephone may not be the most convenient way — unless it’s the appropriate genre — but that clearly wasn’t the goal here anyway. It’s definitely an interesting concept, and we could easily see it transferred to some travel- or spy-themed escape room setting. And speaking of spying, if [Caroline]’s name sounds familiar to you, you may remember her virtual peephole from a few months back.

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A True 4K Projector From Scrap EBay Components

June 22, 2020 by 44 Comments

Cinemas all over the world have become no-go zones with COVID-19 around, but watching the latest blockbuster on the small screen at home is simply not the same. You could bring the big screen home, but buying a quality projector is going to set you back a small pile of cash. Fortunately [Matt] from [DIY Perks] has an alternative for us, demonstrating how to build your own true 4K projector with parts bought off eBay, for a fraction of the price.

The core of the projector is a small 4K LCD panel, which is from a modified Sony smartphone. [Matt] disassembled the phone, removed the backlight from the LCD, which leaves it semi-transparent, and mounted it at a right angle to the rest of the phone body. The battery was also replaced with a voltage regulator to simulate a full battery. To create a practical projector, a much brighter backlight is needed. [Matt] used a 100W 10 mm diameter LED for this purpose. The LED needs some serious cooling to prevent it from burning itself out, and a large CPU cooler does the job perfectly. Two Fresnel lenses in series are used to turn the diverging light from the LED into a converging light source to pass through the LCD. An old 135 mm large format camera lens is placed at the focal point of light to act as a projection lens. The entire assembly is mounted on a vertical frame of threaded rods, nuts, and aluminium plates. [Matt] also used these threaded rods with GT2 pulleys to create a simple but effective moving platform for the projection lens that allows the focus of the projected image to be adjusted. The frame is topped off by a 45-degree mirror to project the image against a wall instead of the roof, and the frame is covered with aluminium panels.

The video after the break goes into incredible detail on how projector functions and how to build your own down. It definitely looks like a doable build for most hackers. [Matt] will also be releasing a complete PDF build guide in the next few weeks. Continue reading “A True 4K Projector From Scrap EBay Components” →