Mathematicians concerned with cryptography need novel ways of generating random numbers in order to securely transmit data such as a credit card number or especially private email.
But it’s hard for computers to generate truly random numbers, as they simply follow whatever instructions you feed it. A computer program is a “deterministic process,” and deterministic processes can be repeated to reproduce the same results. Hardly secure, no?
The delightful arXiv (pronounced “archive”), a collection of scientific papers maintained by Cornell University, reports that Swiss scientists at the University Of Geneva have developed a method of generating truly random numbers using nothing more than a smartphone camera. Because cameras interact with light, they have easy access to the weird world of quantum physics and can be hacked into effective quantum random number generators.
Here’s the explanation of how it works:
Each pixel senses the number of photons that arrive in a certain period of time. These photons are converted into electrons, which are then amplified by a factor determined by the camera’s sensitivity setting (ISO setting). 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.
To simplify this a lot, your smartphone camera can be pointed anywhere to get a light measurement. That data is converted into mathematical language that the phone uses to spit out random digits at the rate of 1 megabit per second, which is sufficient for securing “emails and even phone calls.”
The fact that something as basic as the camera on the smartphone you already have can be harnessed for quantum cryptographic communication will likely have big implications as the technology is further developed. As is written in the arXiv post, “there ought to be significant demand for this kind of service given the wholesale eavesdropping that various states have indulged in recently. So it’s not beyond the realms of possibility that some governments will want to regulate the use of this kind of technology.”
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