Counterfeit chargers for portable electronics are a major problem. At the end of 2016, Apple claimed that of 100 Apple-branded charging accessories it bought on Amazon, 90 were counterfeits. Around the same time, Britain’s Chartered Trading Standards Institute reported that of 400 counterfeit chargers it bought from a range of online retailers, 397 failed a basic safety test.
In the last few years, portable electronics that can be recharged wirelessly have started coming to market. In an effort to get ahead of the problem of counterfeit wireless chargers — which could cause power surges that fry a device’s circuitry — researchers from MIT’s Microsystems Technology Laboratories have built a chip that blocks attempts to wirelessly charge a device’s battery unless the charger first provides cryptographic authentication.
The chip uses an authentication technique called elliptic curve cryptography, which is a “public-key” cryptographic technique. Using publicly available information, the chip can generate — and verify the response to — a question that only a charger with valid private information can answer. The chip doesn’t need to store a secret key of its own.
Elliptic curve cryptography is a well-established technique. But the MIT team has developed a battery of methods for reducing chips’ power consumption, and found a way to simplify the encryption circuit so that it takes up less space on the chip and consumes less power.
