A method and apparatus for generating true random numbers is provided which is hardware based, and which uses unpredictable physical noise produced by an optoisolator. Specifically, the noises resulting from one or more of quantum shot, thermal noise, flicker, and the photoelectric effect are used as variable energy sources for subsequent conversion into a bitstream used for random number selection. The apparatus is preferably provided with a through hole prototype design and construction which requires minimal number of components reducing overall costs.