Archive for November, 2013

the dark side of user interface design

 

 

“A Dark Pattern is a type of user interface that appears to have been carefully crafted to trick users into doing things, such as buying insurance with their purchase or signing up for recurring bills.”

Source 1:

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Instruction-less computing: Doing stuff with a CPU without actually executing instructions

Having fun with hardware is a good way to learn about the machines which soon will become our new overlords. With this pretty interesting presentation you can dive deep into what a CPU does and how it can be exploited to run code by not running it.

Trust Analysis, i.e. determining that a system will not execute some class of computations, typically assumes that all computation is captured by an instruction trace. We show that powerful computation on x86 processors is possible without executing any CPU instructions. We demonstrate a Turing-complete execution environment driven solely by the IA32 architecture’s interrupt handling and memory translation tables, in which the processor is trapped in a series of page faults and double faults, without ever successfully dispatching any instructions. The “hard-wired” logic of handling these faults is used to perform arithmetic and logic primitives, as well as memory reads and writes. This mechanism can also perform branches and loops if the memory is set up and mapped just right. We discuss the lessons of this execution model for future trustworthy architectures.

Bildschirmfoto 2013-11-02 um 01.04.31

Source 1: https://www.usenix.org/conference/woot13/page-fault-weird-machine-lessons-instruction-less-computation

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full text transcripts of the Apple World Wide Developer Conference (wwdc)

Since I’ve become sort of an iOS developer lately I had my fair share of WWDC recordings to get started with this whole CocoaTouch and Objective-C development stuff.

Now a tool that is pretty handy is a this website that offers a full-text transcript search of all WWDC recordings. Awesome!

Bildschirmfoto 2013-11-02 um 00.54.36

Source 1: http://asciiwwdc.com/
Source 2: http://miataru.com/ios

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when DVB-T is not interesting, use the hardware for fun and SDR!

SDR – or Software Defined Radio is relatively cheap and fun way to dive deeper into radio communication.

“Software-defined radio (SDR) is a radio communication system where components that have been typically implemented in hardware (e.g. mixers, filters, amplifiers, modulators/demodulators, detectors, etc.) are instead implemented by means of software on a personal computer or embedded system. While the concept of SDR is not new, the rapidly evolving capabilities of digital electronics render practical many processes which used to be only theoretically possible.” (Wikipedia)

So with cheap hardware it’s possible to receive radio transmissions on all sorts of frequencies and modulations. Since everything after the actual “receiving stuff”-phase happens in software the things you can do are sort of limitless.

Now what about the relatively cheap factor? – The hardware you’re going to need to start with this is a DVB-T USB stick widely available for about 25 Euro. The important feature you’re going to look for is that it comes with a Realtek RTL2832U chip.

“The RTL2832U is a high-performance DVB-T COFDM demodulator that supports a USB 2.0 interface. The RTL2832U complies with NorDig Unified 1.0.3, D-Book 5.0, and EN300 744 (ETSI Specification). It supports 2K or 8K mode with 6, 7, and 8MHz bandwidth. Modulation parameters, e.g., code rate, and guard interval, are automatically detected.

The RTL2832U supports tuners at IF (Intermediate Frequency, 36.125MHz), low-IF (4.57MHz), or Zero-IF output using a 28.8MHz crystal, and includes FM/DAB/DAB+ Radio Support. Embedded with an advanced ADC (Analog-to-Digital Converter), the RTL2832U features high stability in portable reception.” (RealTek)

You’ll find this chip in all sorts of cheap DVB-T USB sticks like this one:

3948543_b6f7670bc7To use the hardware directly you can use open source software which comes pre-packaged with several important/widely used demodulator moduls like AM/FM. Gqrx SDR is available for all sorts of operating systems and comes with a nice user interface to control your SDR hardware.

The neat idea about SDR is that you, depending on the capabilities of your SDR hardware, are not only tuned into one specific frequency but a whole spectrum several Mhz wide. With my device I get roughly a full 2 Mhz wide spectrum out of the device allowing me to see several FM stations on one spectrum diagram and tune into them individually using the demodulators:

Bildschirmfoto 2013-11-01 um 23.28.56The above screenshot shows the OS X version of Gqrx tuned into an FM station. You can clearly see the 3 stations that I can receive in that Mhz range. One very strong signal, one very weak and one sort of in the middle. By just clicking there the SDR tool decodes this portion of the data stream / spectrum and you can listen to a FM radio station.

Of course – since those DVB-T sticks come with a wide spectrum useable – mine comes with an Elonics E4000 tuner which allows me to receive – more or less useable – 53 Mhz to 2188 Mhz (with a gap from 1095 to 1248 Mhz).

Whatever your hardware can do can be tested by using the rtl_test tool:

root@berry:~# rtl_test -t
Found 1 device(s):
0:  Terratec T Stick PLUS

Using device 0: Terratec T Stick PLUS
Found Elonics E4000 tuner
Supported gain values (14): -1.0 1.5 4.0 6.5 9.0 11.5 14.0 16.5 19.0 21.5 24.0 29.0 34.0 42.0
Benchmarking E4000 PLL…
[E4K] PLL not locked for 52000000 Hz!
[E4K] PLL not locked for 2189000000 Hz!
[E4K] PLL not locked for 1095000000 Hz!
[E4K] PLL not locked for 1248000000 Hz!
E4K range: 53 to 2188 MHz
E4K L-band gap: 1095 to 1248 MHz

Interestingly when you plug the USB stick into an Raspberry Pi and you follow some instructions you can use the Raspberry Pi as an SDR server allowing you to place it on the attic while still sitting comfortably at your computer downstairs to have better reception.

If you want to upgrade your experience with more professional hardware – and in fact if you got a sender license – you can take a look at the HackRF project which currently is creating a highly sophisticated SDR hardware+software solution:

jawbreaker-fd0-145436

Source 1: http://www.realtek.com.tw/products/productsView.aspx?Langid=1&PFid=35&Level=4&Conn=3&ProdID=257
Source 2: http://gqrx.dk/
Source 3: www.hamradioscience.com/raspberry-pi-as-remote-server-for-rtl2832u-sdr/
Source 4: http://ossmann.blogspot.de/2012/06/introducing-hackrf.html
Source 5: https://github.com/mossmann/hackrf

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