A Hardware-Embedded Delay Physical Unclonable Function (“HELP PUF”) leverages entropy by monitoring path stability and measuring path delays from core logic macros. Reliability and security enhancing techniques for the HELP PUF reduce bit flip errors during regeneration of the bitstring across environmental variations and improve cryptographic strength along with the corresponding difficulty of carrying out model building attacks. A voltage-based enrollment process screens unstable paths on normally synthesized (glitchy) functional units and reduces bit flip errors by carrying out enrollment at multiple supply voltages controlled using on-chip voltage regulators.