Apparatus and method for generating a random bit sequence

A method for generating a random bit sequence comprising the steps:

• providing a ring oscillator that includes digital switch elements;
• exciting at least two harmonic wave edges of the ring oscillator, which harmonic wave edges form an oscillator signal that fluctuates between two predefined logical levels;
• tapping the oscillator signal;
• and
• determining a random bits as a function of a number of level crossings of the oscillator signal within a predefined period of time.

An apparatus for generating a random bit sequence comprising

• a ring oscillator with a plurality of inverting digital devices and on which an oscillator signal can be tapped, wherein the inverting digital devices comprise an even number of serially connected inverters,
• a buffer element for storing levels of the oscillator signal, wherein the buffer element registering and storing a number of at least one of rising and falling oscillator-signal edges,
• at least two controllable switching devices provided in a signal path of the ring oscillator for simultaneously exciting at least two harmonic wave edges of the ring oscillator, the at least two harmonic wave edges forming the oscillator signal, and
• a control device generating a start signal for the controllable switching devices and buffer element in such a way that every controllable switching device will in each case generate a harmonic wave edge of the oscillator signal and the buffer element will be reset.