Hardware Security Trojan Detection is a verification methodology identifying malicious hardware modifications inserted by adversaries during design, fabrication, or distribution — Hardware Trojans represent subtle modifications to circuit functionality that compromise security, leak sensitive data, or enable system compromise while evading detection. Trojan Characteristics include stealthy triggers activating only under rare conditions, minimal area footprint to avoid detection, and minimal power overhead remaining hidden during normal operation. Detection Methodologies encompass side-channel analysis measuring power consumption and electromagnetic emissions to identify unusual activation patterns, structural analysis comparing layouts against golden references to detect unauthorized modifications, and behavioral testing executing security-sensitive operations to observe anomalous behavior. Side-Channel Approaches analyze power fluctuations from Trojan activation, timing deviations from inserted logic paths, and electromagnetic emissions from additional circuitry. Formal Verification compares hardware specifications against implementations using model checking and theorem proving to identify unauthorized modifications, though scalability limitations constrain application to critical blocks. Test Generation creates test patterns exercising suspicious regions, though Trojans may resist testing through rare trigger conditions. Manufacturing Verification includes wafer-level testing, statistical analysis of parameter variations indicating design anomalies, and reverse engineering inspecting layouts for unauthorized components. Trojan Modeling characterizes trigger mechanisms, payload effects, and activation conditions informing detection strategy design. Hardware Security Trojan Detection requires multi-faceted approaches combining analysis, verification, and testing methodologies.