MSIX establishes a verifiable chain of trust from a running process all the way back to the developer's original signed package. Package identity is embedded in the process token via the WIN://SYSAPPID attribute, which traces back through AppxManifest.xml, AppxBlockMap.xml (containing file hashes), and the package signature. Before installation, Windows validates the signature, block map integrity, and manifest hash consistency. After installation, Package Integrity Content Enforcement (PICE) protects package files on disk using ACLs and Process Trust Label ACEs (TL ACEs), restricting modifications to trusted Windows components like the Deployment engine. Store-signed packages get PICE automatically; other signed packages can opt in via the AppxManifest.xml. This end-to-end runtime trust extension is patented by Microsoft as 'Pervasive package identifiers'.
