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Reusable Secure Architecture Models

This document presents reference models that can be used as a secure basis for new projects.
Each model is associated with:

  • A typical risk level (L1, L2 or L3)
  • The applicable ARC requirements
  • The mitigated threats
  • The suggested .drawio or PlantUML files

🧱 Model 1 - Web Monolith with Internal Backend (Risk L1)​

📝 Description​

  • Traditional application with an internal backend and a local database
  • No public APIs
  • Access controlled via a private network

✔️ Applicable requirements​

  • ARC-001 (Trust zones identified and documented)
  • ARC-007 (Reusable and approved architecture patterns)
  • ARC-010 (Versioned and accessible architecture diagrams)

🔑 Mitigated threats​

  • STRIDE: Tampering, Information Disclosure

🖼️ Suggested diagram​

[UI] --> [Web Server] --> [Database]

⚠️ In this model, control is ensured above all by simplicity and restricted exposure.

☁️ Model 2 - Microservices with External APIs (Risk L2)​

📝 Description​

  • APIs exposed via an authenticated Gateway
  • Microservices with logical segmentation
  • mTLS on internal communication

✔️ Applicable requirements​

  • ARC-001, ARC-002, ARC-003, ARC-004, ARC-005, ARC-006
  • ARC-007, ARC-008, ARC-009, ARC-010

🔑 Mitigated threats​

  • STRIDE: Elevation of Privilege, Spoofing, Repudiation

🖼️ Suggested diagram​

[API Gateway] <--> [Service A] <--> [Service B] <--> [DB]
                      |
                 [Auth Service]

✅ Requires formal technical validation (ARC-005) and threat modelling review (ARC-010).

🧐 Model 3 - Regulated Critical Platform (Risk L3)​

📝 Description​

  • Application subject to regulation (e.g. healthcare, financial)
  • Strict control of boundaries
  • Physical and logical segmentation (Kubernetes namespaces, DMZs)

✔️ Applicable requirements​

  • All requirements ARC-001 to ARC-013

🔑 Mitigated threats​

  • STRIDE: All

🖼️ Suggested diagram​

[Client] --> [Web Gateway] --> [Frontend Pod]
                            --> [Backend Pod] --> [Data Services]

✅ This model requires full application of the chapter, including segmentation between environments (ARC-011), formal approval (ARC-012), automatic topology validation (ARC-013) and end-to-end traceability (ARC-008).

📁 Reuse suggestions​

  • Make the models available in .drawio or .puml in the internal repository
  • Assign a technical owner per model
  • Validate annually and associate with real projects as a reference

These models do not replace the specific design of each application, but they constitute mandatory minimum patterns to be validated according to the risk level.