ARCH EP122

Trust Boundaries Explained: Where Security Decisions Belong DESCRIPTION: Security decisions belong where trust changes. Learn to find trust boundaries between users, proxies, apps and data, why forwarded headers and client claims aren't proof, and where each check must really run. In this episode you'll learn: What a trust boundary is Client claims vs server decisions Proxies, headers and forwarded identity Moving boundaries during design changes Chapters: 0:00 Intro 0:05 An invisible crossing 0:36 Case update input 1:09 Changed assumptions 1:46 Client versus server 2:20 Identity verifier 2:56 Trusted proxy claims 3:30 Machine boundary 4:06 Data versus instructions 4:40 Storage transitions 5:13 AI content authority 5:49 Administrative powers 6:27 Organizational contract 7:03 Alternative routes 7:38 Decision and enforcement 8:12 Trusted decision facts 8:46 Time and freshness 9:22 Dependency failure 9:58 Observed evidence 10:36 Allowed and denied review 11:09 Changed boundaries 11:41 Challengeable assumptions 12:16 Checked transitions 12:50 A receiving component’s decision This is Episode 122 of the Harbor Security Architecture Series — hand-drawn whiteboard explainers that build one concept at a time. Episodes 121–135 follow the fictional company Harbor as it designs an enterprise security architecture: mapping, trust boundaries, threat modeling, attack trees, defense in depth, zero trust, device trust, ZTNA, microsegmentation, mTLS, data protection, third parties, resilience and validation. All people, accounts, identifiers and environments shown are fictional and illustrative; addresses, identifiers and examples are illustrative, and no real certificates, keys, vendor configurations or measured results are displayed. Check your product's documentation before applying any configuration. #ZeroTrust #SecurityArchitecture #CyberSecurity TAGS: trust boundaries, threat modeling, secure design, security architecture, application security, zero trust, enterprise security, cybersecurity, security design, zero trust architecture, cissp, network security, whiteboard animation