HTTP security headers as a semantic policy layer for multichain interoperability

Abstract

Multichain systems increasingly rely on web-based interfaces to expose services, including blockchain gateways, relayers, and wallet-facing applications. Existing interoperability solutions focus on protocol-level mechanisms, neglecting how services are accessed, combined, or isolated at the web interface. Reinterpreting HTTP security headers as a declarative semantic policy layer for multichain interoperability offers a pragmatic solution. Concepts of trust boundaries, isolation properties, and interaction constraints can be expressed through existing header semantics such as Content Security Policy (CSP), Cross-Origin Resource Sharing (CORS), Cross-Origin Opener Policy (COOP), Cross-Origin Embedder Policy (COEP), and Cross-Origin Resource Policy (CORP). To realize such a policy layer, we introduce a lightweight formal policy model and a Semantic Web Security Gateway (SWG) that composes and enforces header-based policies at the web edge, without modifying interoperability protocols. To illustrate how web-layer semantic policies complement native interoperability designs, we use a multichain application scenario. This highlights separation of concerns and supports a defense-in-depth approach.