Flash is designed to last a decade or more of use. A lot of the gadgets that rely on it, however, are not. Shady recyclers have spotted opportunity in that mismatch, stripping out used chips and selling them as new. But fret not, there is something that can be done to address the issue. From a report: Engineers at the University of Alabama have come up with a straightforward electronic examination that can tell if a flash chip is new or recycled, even if that chip has only seen 5 percent or less of its life. And the technique is so straightforward that a smartphone app could run it on its own memory. […] A flash memory cell is like an ordinary transistor, it has a source and a drain and a channel through which current flows under the control of voltage on the gate electrode. The difference is that the gate is split into several layers — the control gate, the blocking oxide, the floating gate, and the tunneling oxide. […] Voltage on the control gate causes electrons to tunnel through that bottom oxide and get stuck inside the floating gate. This charge or its absence is the stored bit. It alters how much voltage you need to turn the transistor on in a way that you can easily measure. Erasing the bit is done by reversing the voltage and driving the charge out of the floating gate. Ray and his team took advantage of the rather high voltages — about plus or minus 20 volts — needed to program and erase flash. The more you program and erase a cell, the more defects will accumulate in the oxide, he explains.

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Source: Slashdot – Engineers Devise a Technique To Fight Counterfeit or Recycled Smartphone Memory