Overview
OpenID AuthZEN (Authorization Exchange) is an emerging standard that defines a common API between Policy Enforcement Points (PEPs) and Policy Decision Points (PDPs), enabling fine-grained, runtime authorization decisions without coupling applications to specific policy engines. Rather than embedding authorization logic in applications or relying solely on OAuth scopes, AuthZEN allows applications to ask "Can subject S perform action A on resource R in context C?" and receive a permit/deny decision from any compliant PDP. This standardization means organizations can swap policy engines (OPA, Cedar, XACML, Zanzibar-style systems) without rewriting application code. AuthZEN represents a shift toward externalized, continuous authorization aligned with Zero Trust principles—moving beyond static token entitlements to real-time, context-aware access decisions.
Architecture & Reference Patterns
Pattern 1: Gateway + Application Dual Enforcement
API gateways perform coarse-grained authorization (route/method checks) while applications make fine-grained AuthZEN calls for resource-level decisions. Both call the same PDP, ensuring consistent policy enforcement. The gateway blocks unauthorized routes early, while applications enforce business-specific rules on domain objects.
Pattern 2: Sidecar PDP with Central Policy
A PDP runs as a sidecar alongside each microservice (similar to OPA's deployment model). Policy bundles are distributed from a central policy administration point, and the sidecar evaluates AuthZEN requests locally for low latency. Applications make localhost AuthZEN calls, avoiding network hops for authorization decisions.
Pattern 3: Centralized PDP Service
A dedicated PDP service handles all authorization requests from across the organization. Provides consistent enforcement and centralized audit logging, but introduces a critical dependency and latency for every authorization decision. Requires high availability design, caching strategies, and circuit breakers.
Pattern 4: Event-Driven Authorization with CAEP/SSF
AuthZEN integrates with the Shared Signaling Framework (SSF) and CAEP to incorporate real-time security events into authorization decisions. When a session is revoked or device compliance changes, the PDP receives signals that affect subsequent authorization evaluations. Enables continuous authorization based on current security posture.
Key Decisions
| Decision | Options | Recommendation | Notes / Gotchas |
|---|---|---|---|
| PDP deployment model | Centralized service, sidecar, embedded library | Sidecar for latency-sensitive; centralized for auditability | Centralized PDP is a single point of failure—invest in HA |
| Policy engine selection | OPA/Rego, Cedar, XACML, Zanzibar-style | Cedar or Rego for new implementations; XACML for legacy | AuthZEN decouples this choice from application code |
| Caching strategy | No caching, decision caching, attribute caching | Attribute caching with short TTL; avoid decision caching for sensitive ops | Decision caching risks stale authorization—be cautious |
| Fallback behavior | Fail-open, fail-closed, cached decision | Fail-closed for security-sensitive; fail-open with logging for non-critical | Fail-open creates security gaps; fail-closed causes outages |
| Batch vs. single requests | Single evaluation, batch evaluations | Batch for list filtering; single for individual access checks | Search APIs help build authorization-aware UIs efficiently |
| CAEP integration | Not integrated, integrated for session events, full SSF | Integrate CAEP for session revocation at minimum | Real-time signals enable continuous authorization |
Implementation Approach
Phase 0: Discovery
Inputs: Current authorization implementations, policy engine landscape, application inventory, compliance requirements, latency requirements Outputs: Authorization patterns assessment, candidate applications for AuthZEN adoption, PDP product evaluation, latency tolerance analysis, integration complexity assessment
Phase 1: Design
Inputs: Discovery outputs, security requirements, performance requirements, audit requirements Outputs: AuthZEN architecture document, PDP deployment design, policy migration plan, subject/action/resource/context schemas, caching strategy, fallback behavior specification, CAEP integration design
Phase 2: Build & Integrate
Inputs: Design documents, PDP infrastructure, pilot applications, policy authoring tools Outputs: PDP deployed and configured, AuthZEN SDK/libraries available, pilot application integrated, batch and search APIs tested, monitoring and decision logging operational
Phase 3: Rollout
Inputs: Tested AuthZEN infrastructure, application migration plan, policy migration plan, training materials Outputs: Applications migrated to AuthZEN in priority order, policies migrated to new PDP, legacy authorization deprecated, performance baselines established, audit logging validated
Phase 4: Operate
Inputs: Production AuthZEN environment, monitoring dashboards, policy governance process Outputs: Policy changes through governed process, authorization analytics for security insights, performance tuning, PDP capacity management, continuous improvement of authorization coverage
Deliverables
- AuthZEN architecture document with PDP deployment design
- Subject/action/resource/context schema definitions
- Policy migration guide from current authorization
- SDK/library selection and integration guide
- Caching and fallback strategy document
- Decision logging and audit requirements
- Performance testing results and baselines
- CAEP/SSF integration specification
Risks & Failure Modes
| Risk | Likelihood | Impact | Early Signals | Mitigation |
|---|---|---|---|---|
| PDP latency impacts application performance | M | M | Slow page loads, authorization timeouts | Sidecar deployment, caching, async authorization where appropriate |
| PDP outage blocks all access | L | H | PDP errors, health check failures | HA deployment, circuit breakers, fail-closed with clear escalation |
| Policy misconfiguration causes access issues | M | H | Users unable to access resources, support tickets spike | Policy testing in CI/CD, staged rollouts, rollback capability |
| Attribute synchronization delays cause stale decisions | M | M | Authorization based on outdated attributes | CAEP integration for real-time updates, short cache TTLs |
| Vendor lock-in despite standard API | M | M | Migration complexity discovered late | Use standard AuthZEN API strictly, avoid proprietary extensions |
| Incomplete migration leaves gaps | H | M | Applications on mixed authorization, inconsistent enforcement | Clear migration roadmap, prioritize high-risk applications |
KPIs / Outcomes
- Authorization decision latency: P99 under 10ms for sidecar, under 50ms for centralized
- PDP availability: Target 99.99% uptime for sidecar, 99.95% for centralized
- Policy coverage: Percentage of authorization decisions through AuthZEN (target: 100% for covered apps)
- Authorization audit completeness: 100% of decisions logged with full context
- Policy deployment frequency: Enable frequent policy updates without application changes
- Authorization-related incidents: Track and trend toward zero