World demand for random number generators is rapidly increasing. Widespread need is found, among others, in the scientific, military, communications and e-commerce fields. With the broadening application spectrum and increasing market volume, the production rate of random number strings from a generator should increase substantially.
Two basic approaches are traditionally followed in the prior art to generate random numbers.
The more common of these is synthetic generation by computer routines. It produces so called “pseudo random numbers”. Generation rates of pseudo random numbers by present routines are indeed fast. However, the pseudo random numbers are intrinsically cyclic and thus limited in bit-length. In essence, the resulting numbers are deterministic and can be easily reproduced by expert cryptologists. Specifically, in the fields of mathematical simulations or in encryption applications the pseudo random numbers are inadequate. They can lead to erroneous results of the simulation analysis or to compromising highly sensitive encrypted information.
The second mode of generation is based on natural occurring chaotic phenomena such as thermal noise in resistors or electronic circuits [see for example Ikeda, Jun, US Patent application US20030050943], radioactive decay [A. Figotin US Patent Application US20030018674], or light transmission or reflection from a beam-splitter [J. Soubusta et al. Proceedings, SPIE, 4356, 54-60, (2001)]. In most true random number generators the physical phenomena exploited in constructing the random numbers are thermodynamic or quantum mechanical in nature, thus exhibiting innate statistical fluctuations. Such chaotic phenomena will produce true random numbers, provided technical limitations such as limited amplifier bandwidth, interference from external sources or cyclic phenomena in the electronics system do not perturb the chaotic nature of the source. For example, true random number generators (TRNG) based on elements that produce thermal noise derive the data from very low signals. They suffer from problems of limited bandwidth of the high gain amplifiers, as well as 1/f amplifier noise that interferes with the extracted noise characteristics of the source. Moreover, TRNG are usually slow. The high value of entropy content is offset by the slow rate of number construction. Consequently, prior art number generation rates fail to satisfy increasing customer demand. Another class of TRNG uses radioactive decay as the source for producing non-correlated strings of numbers. In principle, TRNG using radioactive decay can be very fast, but since it is based on a strong radioactive source, safety issues come into play.
One version of thermionic type TRNG, using photon counting of light emission from a black body radiator, is presented in a patent application by M. J. Klass (Random Number Generator, US Patent Application 20030131031). The photon detector depicted in this application is a special type of photomultiplier tube (PMT). Besides the principal operational scheme of photon counting the authors add an option of using a needle mounted inside the detector that serves as a source of electrons. The claims state that the needle can be metallic, or coated with a dielectric of selected electron emission. The information presented concerning the mode of operation of the needle is rather vague. In one mode a gas breakdown should form, due to the electric field on the needle. A second mode is supposedly related to electron generation by the needle. However, electron field emission by either a metallic needle or a coated needle is a very weak phenomenon. By and large, specially coated needles are by far superior electron emitters than simple metallic needles. Yet, even coated needles must be heated to very high temperatures in order to constitute useful electron sources, but no heating scheme is discussed. Moreover, introducing a high temperature electron source inside a PMT is in itself very problematic for tube operation. Thus, it is safe to assert that the suggested needle source of electrons is a poor choice, if at all feasible.