True random number generators including fibonacci-galois ring oscillators with a stochastic start-up condition

A true random number generator circuit comprising:

• at least one Fibonacci ring oscillator circuit including a first oscillating loop comprising at least three inverter stages, wherein the first oscillating loop is configured to provide a first start-up stochastic condition for starting oscillations in a second oscillating loop, wherein the second oscillating loop comprises a first chain of inverter stages and a first plurality of switches whose state is determined by a first feedback polynomial, wherein the at least one Fibonacci ring oscillator circuit is to:
• (1) during a first mode of operation of the at least one Fibonacci ring oscillator circuit, enable oscillations in the first oscillating loop while keeping the second oscillating loop open, and thereby generate the stochastic start-up condition for starting oscillations in the second oscillating loop, and (2) during a second mode of operation of the at least one Fibonacci ring oscillator circuit, enable oscillations in the second oscillating loop in response to the first stochastic start-up condition, while keeping the first oscillating loop open;
• and
• at least one Galois ring oscillator circuit including a third oscillating loop comprising at least three inverter stages, wherein the third oscillating loop is configured to provide a second start-up stochastic condition for starting oscillations in a fourth oscillating loop, wherein the fourth oscillating loop comprises a second chain of inverter stages and a second plurality of switches whose state is determined by a second feedback polynomial, wherein the at least one Galois ring oscillator circuit is to:
• (1) during a first mode of operation of the at least one Galois ring oscillator circuit, enable oscillations in the third oscillating loop while keeping the fourth oscillating loop open, and thereby generate the second stochastic start-up condition for starting oscillations in the fourth oscillating loop, and (2) during a second mode of operation of the at least one Galois ring oscillator circuit, enable oscillations in the fourth oscillating loop in response to the second stochastic start-up condition, while keeping the third oscillating loop open.

A method for operating a ring oscillator circuit comprising:

• (1) a first oscillating loop including at least two inverter stages, and (2) a second oscillating loop including a chain of inverter stages and a plurality of switches whose state is determined by a feedback polynomial, the method comprising:
• during a first mode of operation of the ring oscillator circuit, generating a stochastic start-up condition by enabling oscillations in the first oscillating loop while keeping the second oscillating loop open;
• and
• during a second mode of operation of the ring oscillator circuit, enabling oscillations in the second oscillating loop in response to the generated stochastic start-up condition, while keeping the first oscillating loop open.