The rapid growth of the Internet of Things (IoT) has increased demand for secure device authentication, driving interest toward hardware cryptography using physical unclonable functions (PUFs) rather than software keys vulnerable to hacking. Block copolymer (BCP) self-assembly is ideal for PUF fabrication, as its thermally driven microphase separation generates unique nanopatterns. Here, we present a multilayer PUF wherein two Pt lamellae are electrically connected and cloning prevented by a rGO "replication-barrier" interlayer. A metal pattern fabricated from a BCP template was coated with rGO, and capped with a second Pt lamella to form a final structure. Electrical measurements verified interlayer conduction with distinct PUF-specific resistances. The rGO layer blocked imprinting and etching-based replication attacks, including resistance shifts for protection. This PUF significantly enhances anti-cloning security, highlighting potential for next-generation nano-security.