Smartphone Cameras Can Be Used as Quantum Random Number Generators

Random numbers fuel our digital lives, but they're notoriously difficult to generate properly. Now, scientists have shown that smartphone cameras can be used as quantum random number generators—and it could change the face of mobile security.

The problem, you see, is that true random numbers can't be generated by deterministic processes—like software on a computer—because the whole point of that kind of process is that it can, by definition, be repeated. Now, though, a team of physicists have been using a Nokia N9 smartphone, along with knowledge of the laws of quantum mechanics, to generate truly random numbers, reports the arXiv Blog.

The gold standard of random number generation is the quantum random number generator, which uses the phenomenon of quantum mechanics to produce strings of entirely random digits. But doing that cheaply and easily has been... a challenge.

But using mobile phone cameras—which have improved so much in recent years that they're now apparently capable of detecting the quantum variations in the number of photons they detect—means that's about to change. The arXiv Blog explains what researchers at the University of Geneva in Switzerland have done:

The quantum process that these guys exploit is the way light sources emit photons. Because each emission is a quantum process, the instant of emission cannot be predicted. So the number of photons that a light source emits in a unit of time will always vary by an amount that is entirely random.

It's straightforward to calculate the average number of electrons this process should produce, given the probabilistic nature of photon emission. But the actual number of electrons should differ by a number that is random. That produces a single random digit. And since a light-sensitive array consists of many pixels working in parallel, it is possible to generate a large quantity of random digits from each image.

They tested the theory out using a Nokia N9 smartphone, which features a pretty ordinary 8 megapixel rear-facing colour camera. Capable of generating numbers at a rate of 1 megabit per second, the phone-based system has turned out to be pretty good. "If everybody on earth used such a device constantly at 1Gbps, it would take 10^80 times the age of the universe for one to notice a deviation from a perfectly random bit string," claim the researchers.

That's impressive, and the results beat all the test that mathematicians have created to spot weaknesses in random numbers in the past. And the applications are pretty exciting: while it would provide true random number encryption of data like credit card numbers, a 1 Mbps generation rate could also means true random number encryption of emails and even phone calls could be possible, too. Just don't ask about battery life. [arXiv via arXiv Blog]

Image by David under Creative Commons license