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Shielding MAC addresses from stalkers is hard and Android fails miserably at it

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Enlarge (credit: Christiaan Colen)

In early 2015, architects of Google’s Android mobile operating system introduced a new feature that was intended to curtail the real-time tracking of smartphones as their users traversed retail stores, city streets, and just about anywhere else. A recently published research paper found that the measure remains missing on the vast majority of Android phones and is easily defeated on the relatively small number of devices that do support it.

Like all Wi-Fi-enabled devices, smartphones are constantly scanning their surroundings for available access points, and with each probe, they send a MAC—short for media access control—address associated with the handset. Throughout most of the history of Wi-Fi, the free exchange of MAC addresses didn’t pose much threat to privacy. That all changed with the advent of mobile computing. Suddenly MAC addresses left a never-ending series of digital footprints that revealed a dizzying array of information about our comings and goings, including what time we left the bar last night, how many times we were there in the past month, the time we leave for work each day, and the route we take to get there.

Eventually, engineers at Apple and Google realized the potential for abuse and took action. Their solution was to rotate through a sequence of regularly changing pseudo-random addresses when casually probing near-by access points. That way, Wi-Fi devices that logged MAC addresses wouldn’t be able to correlate probes to a unique device. Only when a phone actually connected to a Wi-Fi network would it reveal the unique MAC address it was tied to. Apple introduced MAC address randomization in June 2014, with the release of iOS 8. A few months later, Google’s Android operating system added experimental support for the measure. Full implementation went live in March 2015 and is currently available in version 5.0 through the current 7.1; those versions account for about two-thirds of the Android user base.

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X-rays let you see the smallest feature buried in your CPU

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The Apple A8 die shot as mapped out by Chipworks. (credit: Chipworks)

The semiconductor industry is beyond remarkable when it comes to the complexity and precision of processes. A modern integrated circuit is not a single layer of circuitry, but many layers, all stacked on top of each other. This is all done through photolithography, where a pattern is imaged on a silicon wafer. Each layer requires a separate image, and all the images have to be aligned. If you take the 14nm number seriously (a nanometer is 1/1,000,000th of a millimeter), then wafers and masks, which are seriously hold-in-two-hands-big, have to be aligned with a precision that is better than the feature size. But, how do you know you’ve done it right?

The obvious answer is whether or not the chip works. But it would be nice to image the circuit so that it can be compared to the design. Apart from detecting problems during manufacturing, being able to image the final product would also allow for the design to be improved, since it would let you identify areas of a chip that consistently cause problems. But, how do you image structures that might be as small as 14nm that are buried under other structures that you also want to image?

The answer, it seems, is a form of X-ray tomography.

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Early Snapdragon 835 benchmarks show mixed results from semi-custom design

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(credit: Qualcomm)

When it announced the Snapdragon 835, Qualcomm promised that the latest in its family of ARM systems-on-chips would boost performance by 27 percent with a 40 percent reduction in power consumption. The first early benchmarks of the processor that Qualcomm doesn’t want us to call a processor have been run and the results are… well, they’re a little uneven.

Anandtech went to Qualcomm’s San Diego headquarters and was shown the 835 running in a hardware platform reference—a basic smartphone built around the chip that serves as a platform for hardware testing and software development. During this visit, they were able to run a handful of basic benchmarks to gauge the performance of the new chip.

Naively, one would assume that Snapdragon 835 would be faster than the 820/821 that went before it. 835 is, after all, a higher number than 820, and higher numbers usually mean better when it comes to processors. But the situation with the 835 is more complicated than that. In the early days of the modern smartphone era, Qualcomm’s 32-bit ARM Snapdragon chips were generally best-in-class. While many ARM chips use core designs that are developed by ARM itself in the UK, Qualcomm did something different; it had a pair of custom designs, Scorpion in 2008 and Krait in 2012, developed in house. These designs were broadly superior to ARM’s Cortex-A8, A9, and A15 designs that other companies were using.

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