# Signed System Volume The Signed System Volume is the cryptographically sealed macOS system volume introduced with macOS 11. System files are covered by a hierarchy of hashes whose root is signed; the seal is checked as part of startup trust. ## Security role SSV moves system integrity beyond ordinary filesystem permissions and [[System Integrity Protection]]. A modification to sealed system content should change the cryptographic root and prevent the altered volume from being accepted under the expected boot policy. On Apple silicon, the SSV participates in a larger chain that includes secure boot, LocalPolicy, Secure Enclave state, system-paired firmware, and kernel collections. ## Evidentiary boundary SSV narrows the historical [[InstallESD.dmg]] attack model but does not eliminate transition vulnerabilities. Modern investigation shifts toward authenticated update parsing, recoveryOS, privileged daemons, reduced-security modes, ownership transitions, and policy authorization. ## Relationships [[Android Verified Boot]] · [[Boot Startup Security]] · [[Hardware Root of Trust]] · [[System Integrity Protection]] · [[InstallESD.dmg]]. ## Source [[InstallESD.dmg#Modern architectural evolution|InstallESD.dmg — modern architectural evolution]].