A true random number generator (TRNG) uses an analog circuit with a ring oscillator configured to collapse from an unstable oscillation state to a stable oscillation state at a random collapse time and counter counting a counter value representing the random collapse time. Various techniques are used to harden the TRNG including a truncator generating a true random number based on a truncation of the reference count value and a dedicated voltage regulator supplying power to the analog core including the ring oscillator. Techniques also include various solutions for drawing a constant current such as using a Gray code counter and adding noise current during and/or after the collapse event with a dummy inverter chain. Bit churning, bit obfuscation entropy enhancers and various post processing techniques may be employed to further harden the TRNG. An attack detection module may raise alerts when the TRNG is being attacked.