Post-Quantum Decentralized Policy Enforcement Points in MCP Node Clusters

Traditional centralized Policy Enforcement Points (PEPs) in MCP node clusters are vulnerable to quantum computing threats, particularly harvest-now-decrypt-later attacks. The post advocates moving to decentralized, node-level enforcement using lattice-based post-quantum algorithms like Kyber (key encapsulation) and Dilithium (signatures). It introduces a 4D security framework (Defense, Detection, Decision, Dynamic Response) using gossip protocols for distributed threat sharing, parameter-level access restrictions to prevent tool poisoning, and hybrid classical/PQC encryption as a transitional strategy. Key management via Shamir's secret sharing and automated rotation is also covered, along with a Python code snippet illustrating decentralized PEP middleware logic.