Structural Cryptography is a novel cryptographic paradigm that leverages continuous resonance functions to replace traditional discrete mathematical constructs like RSA and ECC. Beyond classical message authentication, we introduce a behavior-bound signature model, where each signature corresponds to a verifiable position in structure space and proves compliance with a dynamic trajectory constraint. By deriving personalized struc- ture functions from private keys and attaching zero-knowledge proofs (ZKPs), signatures reflect not only identity but also spatiotemporal behavior. This framework enables offline, privacy-preserving verification of actions taken by autonomous agents—such as robots or IoT devices—without requiring surveillance or state reconstruction. We provide rigorous security analysis, resistance to quantum attacks, and a reference implementation, posi- tioning Structural Cryptography as the first behavior-bound, structure-anchored signature framework offering a cryptographic foundation for verifiable autonomy and post-quantum behavioral security.