Portable true random number generator for personal encryption application based on smartphone camera

The true random number generator (TRNG) is an invaluable resource for many applications. Present TRNG methods all require specialised and expensive hardware, which are not suitable for personal use. A portable TRNG configuration is proposed, which is simply based on the camera of a commercial smartphone. No other auxiliary equipment except the mobile phone itself was needed, which offers a promising solution for personal encryption applications. With the flash lamp of the camera and the thumb of the operator, quasi-uniform illumination was obtained, setting the image sensor at a working point where the shot noise of the photocurrent dominates the overall characteristics of the sensor output noise. Random bits were first produced according to the shot noise and then entropy enhanced by vector-matrix multiplication. A sequence of 10⁹ bits was produced and its randomness has been proved by the National Institute of Standards and Technology (NIST) tests.