  Random numbers are commonly used in many different fields, ranging from
simulations in fundamental science to security applications. In some critical
cases, as Bell's tests and cryptography, the random numbers are required to be
both secure (i.e. known only by the legitimate user) and to be provided at an
ultra-fast rate (i.e. larger than Gbit/s). However, practical generators are
usually considered trusted, but their security can be compromised in case of
imperfections or malicious external actions. In this work we introduce an
efficient protocol which guarantees security and speed in the generation. We
propose a novel source-device-independent protocol based on generic Positive
Operator Valued Measurements and then we specialize the result to heterodyne
measurements. The security of the generated numbers is proven without any
assumption on the source, which can be even fully controlled by an adversary.
Furthermore, we experimentally implemented the protocol by exploiting
heterodyne measurements, reaching an unprecedented secure generation rate of
17.42 Gbit/s, without the need to take into account finite-size effects. Our
device combines simplicity, ultrafast-rates and high security with low cost
components, paving the way to new practical solutions for random number
generation.
