Washington: Radio frequency signals given off by electronic devices like laptops and smartphones can be used to uniquely identify even identical gadgets in the same way as fingerprints can differentiate humans, Disney researchers say.


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The new method, called EM-ID, can differentiate in most cases between devices of the same make and model.


"The idea that these electronic devices have such distinctive radio frequency (RF) emissions is astounding," said Jessica Hodgins, vice president at Disney Research.


"Our researchers were able not only to discover this phenomenon, but to develop a means of using it to identify devices right out of the box," said Hodgins.


Previous work by Disney Research's Chouchang Yang, Alanson P Sample and colleagues has shown that the electromagnetic (EM) noise emitted by most electronic devices is distinctive enough that it can be used to distinguish between general classes of objects - power tools, computers, household appliances, automobiles and more.


The new research shows that it is even possible to use these spurious EM signals to differentiate between objects of the same make and model.


"Electromagnetic emissions are highly structured and a direct manifestation of the circuits that generate them," Yang said.


"But variations in the manufacturing of all components and in final assembly create differences in the EM signal that enable us to differentiate, for example, a laptop computer from another laptop of the same make and model," said Yang.


"Since the EM signature of a given device is an emergent statistical property and not designed to be a unique ID, it is possible that the EM spectrums may overlap, making it hard to identify some objects," said Sample, leader of Disney Research's Wireless Systems group.


In testing, the researchers found that they could successfully identify individual devices with 95 per cent accuracy - ranging from 72 per cent accuracy for the iPhone 6 to 100 per cent accuracy for toy light sabers.


"But even though we can't ensure that EM-IDs are always unique, we have a reliable algorithm for predicting the identification success rate," Sample said.


"So when a new device is registered and entered into an inventory system, it can alert the user whether the device's EM-ID is unique enough to be read or if an alternative strategy is needed," said Sample.


Another limitation is that the device must be powered on and actively emitting the EM signals for the identification method to work.


The EM-ID system uses a low-cost software-defined radio as a reader. The EM signals are digitised and sent to a host computer, where the signals are processed to remove low-magnitude EM noise, leaving a number of frequency peaks that typically include between 1,000 and 2,000 elements.