Improved Hourglass Entropy

January 25, 2013 by Mike Szczys 16 Comments

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[Wardy] built himself a high quality entropy source with parts he had lying around. It’s based on the hourglass entropy project we saw in a links post earlier this month. Just like that project, he is bouncing a laser off of the falling sand and reading the result. But he brings a few innovations to the party, and has test results to back up his work.

The first change is an obvious one; motorize the hourglass so that you don’t need to flip it by hand. We thought this might mess with the laser alignment but the clip after the break proved us wrong. He changed up the sensor, using an LED connected to the base of an NPN transistor. The next change was to mount the light sensor at an angle to the laser rather than straight on. This picks up reflections of the laser and not the direct beam itself, resulting in a wider range of readings.

He used an Ethernet shield to get the system on the network. It’s pushing 420k random numbers per second and was tested with the DieHarder suite. It didn’t get a very high score, but it did pass the test.

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An Attempt To Replace Multiple RFID Cards With A Single Hacked-together Tag

January 21, 2013 by Mike Szczys 31 Comments

It’s kind of a convoluted title, but [Hudson’s] attempt to replace multiple HID Prox cards with one AVR chip didn’t fully pan out. The project started when he wanted to reduce the number of RFID access cards he carries for work down to just one. The cards use the HID Proximity protocol which is just a bit different from the protocols used in most of the hobby RFID projects we see. He ended up taking an AVR assembly file that worked with a different protocol and edited it for his needs.

The device above is the complete replacement tag [Hudson] used. It’s just an AVR ATtiny85 and a coil made of enameled wire. The coil pics up current from the card reader’s magnetic field, and powers the chip through the leakage on the input pins (we’ve seen this trick a few times before). The idea he had was to store multiple codes on the device and send them all in a row. He was able to get the tag to work for just one code, but the particulars of the HID Prox reader make it difficult if not impossible to send multiple codes. The card must send the same code twice in a row, then be removed from the magnetic field before the reader will poll for another combination.

Brute Force Finds The Lost Password For An Electronic Safe

January 21, 2013 by Mike Szczys 24 Comments

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[Teatree] tells a sad, sad story about the lost password for his fire safe. The electronic keypad comes with a manufacturer’s code as well as a user selected combination. Somehow he managed to lose both of them, despite storing the user manual safely and sending the passwords to himself via email. He didn’t want to destroy the safe to get it open, and turning to the manufacturer for help seemed like a cop-out. But he did manage to recover the password by brute forcing the electronic keypad.

There is built-in brute force protection, but it has one major flaw. The system works by enforcing a two-minute lockout if a password is entered incorrectly three times in a row. But you can get around this by cutting the power. [Teatree] soldered a relay to each set of keypad contacts, and another to the power line and got to work writing some code so that his Arduino could start trying every possible combination. He even coded a system to send him email updates. Just six days of constant attacking netted him the proper password.

Breaking The Minteye Captcha Again

January 19, 2013 by Brian Benchoff 16 Comments

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A few days ago we saw a post from [samuirai] at the Shackspace hackerspace in Stuttgart on breaking the minteye captcha system. Like most other captcha cracks, [samuirai] used the voice accessibility option that provides an audio captcha for blind users. Using the accessibility option is a wonderful piece of work, but [Jack] came up with an even more elegant way to defeat the minteye captcha.

For those unfamiliar, the minteye captcha provides a picture tossed through a swirl filter with a slider underneath. Move the slider left or right to eliminate the swirl and you’ve passed the, “are you human” test. Instead of looking for straight lines, [Jack] came up with a solution that easily defeats the minteye captcha in 23 lines of Python: just minimize the length of all the edges found in the pic.

The idea behind the crack is simply the more you swirl an image, the longer the edges in the image become. Edge detection is a well-studied problem, so the only thing the minteye cracking script needed to do was to move the slider for the captcha from the left to the right and measure the lengths of all the edges.

[Jack] included the code for image processing part of his crack, fortunately leaving out the part where he returns an answer to the minteye captcha. For that, and a very elegant way to crack a captcha, we thank him.

Script Defeats Minteye CAPTCHA

January 16, 2013 by Mike Szczys 41 Comments

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We hadn’t heard of minteye CAPTCHA before, but we’ve seen evidence of a script that can break the system. Minteye combines two things which you probably don’t love about the Internet: advertisements and CAPTCHA. The system uses a slider to distort an advertiser’s image. Once the slider is in just the right spot the image becomes clear and you can click on submit to see if you passed the challenge.

Challenges like this are impossible for the visually impaired, so there is usually an audio option as well. In this case the audio button will instruct you to move the slider to the right, left, or that it’s already in the correct place. [Samuirai] used the text2speech API available in Google Chrome to parse these commands. As you can see above, “movies later” is a misinterpretation of “move the slider”, but he was still able to get enough accuracy to solve the challenge. See the script in action in the video after the break.

Audio challenges have been exploited like this in the past. Check out this talk about beating reCAPTCHA through the audio option.

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A Steampunk Combination Sketchbook

January 16, 2013 by Brian Benchoff 28 Comments

[Admiral Aaron Ravensdale], fine craftsman of steampunk wares, just finished up a new project. It’s a sketchbook protected by two layers of security, covered in gilded leather and drenched in the expositions of a [Jules Verne] novel.

The first layer of security for this sketchbook is a combination lock. On the cover are four switches, each with four positions. These are connected to a PICAXE microcontroller which goes to the next stage of the lock once the correct combination is entered.

The book’s security also includes a knock sensor. With a small piezo element hidden under the cover, [Ravensdale] deeds to tap the book with a specific pattern before it opens. The mechanical part is a small hobby servo also mounted to the cover that releases a pair of brass clasps once both locks are opened.

Like all of the [Admiral]’s builds, it’s a fine piece of craftsmanship, equally well suited to take on a holiday with the baron or to the opium dens of Ceylon.

You can check out [Admiral Ravensdale]’s demo of his sketchbook after the break.

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Unsigned Code Running On Windows RT

January 9, 2013 by Mike Szczys 32 Comments

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A crack has been found in the armor of Windows RT. This subset of Windows 8 is designed to run on ARM processors. The payload listed in the image above allows you to run unsigned desktop applications on the OS.

We haven’t seen very much about the Windows RT package, so it’s nice to hear [Clrokr’s] thoughts on it. As far as he can tell the system has not been watered down from its Intel-aimed (x86) counterpart. Rather, RT seems to be a direct port with what is called “Code Integrity” mechanisms switched on. There is a kernel-level setting, barricaded behind UEFI’s Secure Boot, which determines the minimum software signing level allowed to run on the device. This is set to zero on a Windows 8 machine, but defaults to 8 on an ARM device. [Clrokr] uses a debugger to insert the code seen above into a DLL file in order to reset that minimum signing value to 0.

Do you have a project in mind for which this is useful? We’d love to hear about it in the comments!

[via Reddit]