phase-4-trust-boundaries

name	phase-4-trust-boundaries
description	Phase 4 Trust Boundary Analysis guide. Use when defining trust zones, crossing points, and security boundaries between system components.

Phase 4: Trust Boundary Analysis

Objective

Identify where trust levels change in the system. Every crossing point is a potential attack surface that needs security controls.

Concepts

• Trust Zone: A region where components share the same trust level
• Crossing Point: Where data flows between zones (requires authentication/authorization)
• Trust Boundary: The security perimeter with specific controls

Tools Reference

add_trust_zone(name, trust_level, description)

Parameter	Values
trust_level	Untrusted, Low, Medium, High, Full

add_component_to_zone(zone_id, component_id)

Assign a component to exactly one trust zone.

add_crossing_point(source_zone_id, destination_zone_id, authentication_method, authorization_method, description)

Parameter	Values
authentication_method	Password, Multi-factor, Certificate, Token, Biometric, API Key, IAM Role, OAuth, None, Other
authorization_method	Role-based, Attribute-based, Discretionary, Mandatory, Policy-based, Rule-based, None, Other

add_conn_to_crossing(crossing_point_id, connection_id)

Map existing connections to crossing points.

add_trust_boundary(name, type, crossing_point_ids, controls, description)

Parameter	Values
type	Network, Process, Physical, Container, Virtual Machine, Account, Other
crossing_point_ids	List of crossing point IDs
controls	List of security control names (strings)

Other Phase 4 Tools

• list_trust_zones(), list_crossing_points(), list_trust_boundaries()
• get_trust_boundary_detection_plan() -- AI-powered boundary detection
• get_trust_boundary_analysis_plan() -- Security analysis guidance

Common Trust Zone Patterns

Web Application

Zone	Trust Level	Components
Internet	Untrusted	End users, external APIs
DMZ	Low	Load balancer, CDN, WAF
Application	Medium	App servers, API services
Data	High	Databases, caches, queues
Admin	Full	Admin consoles, CI/CD

Microservices

Zone	Trust Level	Components
Public	Untrusted	API Gateway, public endpoints
Service Mesh	Medium	Internal microservices
Data Layer	High	Databases, object stores
Secrets	Full	KMS, secret managers

Workflow

1. Call get_phase_4_guidance()
2. Call get_trust_boundary_detection_plan() for AI-guided detection
3. Create trust zones based on security domains
4. Assign components to zones with add_component_to_zone()
5. Define crossing points where data flows between zones
6. Map connections to crossing points with add_conn_to_crossing()
7. Create trust boundaries with security controls

Completion Criteria

• All trust zones defined
• Every component assigned to a zone
• Crossing points defined for all inter-zone communication
• Connections mapped to crossing points
• Trust boundaries created with controls listed
• Call advance_phase() to proceed to Phase 5

Common Pitfalls

• Putting everything in one trust zone
• Missing the boundary between internal services and external APIs
• Not specifying authentication/authorization at crossing points
• Forgetting admin/management plane boundaries