A method of operating a ring oscillator used for generating and providing random numbers data for a security application, the ring oscillator comprising a plurality of logic gates (201, 202, 203, 204) connected in a ring configuration in which an output of each except a last of the plurality of logic gates (201, 202, 203, 204) is used as an input for a next one of the plurality of logic gates, the output of the last of the plurality of logic gates being fed back to and used as an input for a first of the plurality of logic gates, the method comprising: starting the ring oscillator by a ring-enable signal provided to one of the plurality of logic gates (201, 202, 203, 204) in the ring configuration and a clock signal provided to a clock input of at least one controlled logic gate of the plurality of logic gates (201, 202, 203, 204) in the ring configuration, the at least one controlled logic gate receiving the clock signal to control the at least one controlled logic gate and thereby synchronize the ring oscillator to the clock signal, the clock signal being provided to the clock input for a predetermined warm-up duration; and after the predetermined warm-up duration, restarting and operating the ring oscillator without the clock signal by removing or disabling the clock signal, wherein the restarting and operating of the ring oscillator without the clock signal comprises the following: disabling the ring oscillator; stopping or removing the clock signal; waiting for a first predetermined period of time; restarting the oscillator in free running mode without the clock signal; waiting for a second predetermined amount of time; obtaining desired data from the ring oscillator for the security application. starting the ring oscillator by a ring-enable signal provided to one of the plurality of logic gates (201, 202, 203, 204) in the ring configuration and a clock signal provided to a clock input of at least one controlled logic gate of the plurality of logic gates (201, 202, 203, 204) in the ring configuration, the at least one controlled logic gate receiving the clock signal to control the at least one controlled logic gate and thereby synchronize the ring oscillator to the clock signal, the clock signal being provided to the clock input for a predetermined warm-up duration; and after the predetermined warm-up duration, restarting and operating the ring oscillator without the clock signal by removing or disabling the clock signal, wherein the restarting and operating of the ring oscillator without the clock signal comprises the following: disabling the ring oscillator; stopping or removing the clock signal; waiting for a first predetermined period of time; restarting the oscillator in free running mode without the clock signal; waiting for a second predetermined amount of time; obtaining desired data from the ring oscillator for the security application. disabling the ring oscillator; stopping or removing the clock signal; waiting for a first predetermined period of time; restarting the oscillator in free running mode without the clock signal; waiting for a second predetermined amount of time; obtaining desired data from the ring oscillator for the security application.