From the 'tech' page: > "...it has a pair of devices that are wired up in such a way that as a high potential is applied across them, where electrons do not no

From the 'tech' page: > "...it has a pair of devices that are wired up in such a way that as a high potential is applied across them, where electrons do not normally flow in this direction and would be blocked, the high voltage compresses the semiconduction gap sufficiently that the occasional stray electron will quantum tunnel through the P-N junction. (This is sometimes referred to as avalanche noise.) When this happens is unpredictable, and this is what the Entropy Key measures." 'Unpredictable' would qualify as random.