This article presents an all-silicon multidimensionally-encoded optical physical unclonable function (PUF) for integrated circuit anti-counterfeiting. The PUF is fabricated by integrating silicon metasurfaces with erbium-doped silicon quantum dots (Er-Si QDs) using a CMOS-compatible process. The PUF generates five in-situ optical responses within a single pixel, achieving an ultrahigh information entropy of 2.32 bits/pixel. These responses include micropattern imaging, photoluminescence intensity of Si QDs, photoluminescence intensity of Er³+, photoluminescence wavelength of Si QDs, and photoluminescence lifetime of Si QDs. The position-dependent optical responses arise from the radiation field and Purcell effect. The PUF's performance is evaluated using metrics such as bit uniformity, similarity, intra- and inter-Hamming distances, false-acceptance and rejection rates, and encoding capacity. The PUF is used to implement efficient lightweight mutual authentication protocols for IoT applications. The PUF is also shown to be robust against extreme conditions such as heating, laser exposure, abrasion, and UV radiation. The PUF's stability and high information entropy make it suitable for anti-counterfeiting applications in IoT systems. The PUF is fabricated using a CMOS-compatible process, making it scalable and cost-effective for large-scale production. The PUF's unique optical responses enable the generation of multiple cryptographic keys, enhancing security through multifactor authentication. The PUF's performance is validated through simulations and experiments, demonstrating its potential for secure identification and authentication in IoT systems.This article presents an all-silicon multidimensionally-encoded optical physical unclonable function (PUF) for integrated circuit anti-counterfeiting. The PUF is fabricated by integrating silicon metasurfaces with erbium-doped silicon quantum dots (Er-Si QDs) using a CMOS-compatible process. The PUF generates five in-situ optical responses within a single pixel, achieving an ultrahigh information entropy of 2.32 bits/pixel. These responses include micropattern imaging, photoluminescence intensity of Si QDs, photoluminescence intensity of Er³+, photoluminescence wavelength of Si QDs, and photoluminescence lifetime of Si QDs. The position-dependent optical responses arise from the radiation field and Purcell effect. The PUF's performance is evaluated using metrics such as bit uniformity, similarity, intra- and inter-Hamming distances, false-acceptance and rejection rates, and encoding capacity. The PUF is used to implement efficient lightweight mutual authentication protocols for IoT applications. The PUF is also shown to be robust against extreme conditions such as heating, laser exposure, abrasion, and UV radiation. The PUF's stability and high information entropy make it suitable for anti-counterfeiting applications in IoT systems. The PUF is fabricated using a CMOS-compatible process, making it scalable and cost-effective for large-scale production. The PUF's unique optical responses enable the generation of multiple cryptographic keys, enhancing security through multifactor authentication. The PUF's performance is validated through simulations and experiments, demonstrating its potential for secure identification and authentication in IoT systems.