PCI DSS Scope Reduction Strategies

The principle is simple: if a system doesn't touch cardholder data and isn't connected to one that does, it's out of scope. Your goal is to shrink your CDE to the absolute minimum.

Key Takeaways

Understanding PCI DSS Scope

What's in Scope?

Three categories of systems are in scope for PCI DSS:

The Scope Expansion Problem

Without careful architecture, scope expands rapidly:

1CDE Database
2  ↓ connects to
3Backup Server
4  ↓ connects to
5Backup Management Server
6  ↓ connects to
7Corporate Network
8  ↓
9All workstations now in scope (!)

This is why scope reduction matters. Every connection to the CDE potentially adds systems to your compliance scope.

Strategy 1: Tokenization

Tokenization replaces sensitive cardholder data with non-sensitive tokens. The actual card data is stored by a PCI-compliant token service provider.

How Tokenization Works

1Customer enters card → Payment processor → Token returned → You store token only

Your systems never store the PAN. You store a token that references the card at your payment processor.

Tokenization Benefits

Implementation Considerations

Choosing a token format:

• Format-preserving: Tokens look like card numbers (same length, pass Luhn check)
• Random: Completely random strings
• Reversible vs irreversible: Can you get the PAN back, or only charge through the token

Stripe/Adyen tokens:

• Automatically provided when using their payment forms
• Can only be used with that processor
• Stored securely in their systems

Important: Tokenization reduces scope but doesn't eliminate it entirely. You still have obligations for how you handle tokens and integrate with the token service.

Strategy 2: Network Segmentation

Network segmentation isolates your CDE from the rest of your network, preventing connected systems from expanding your scope.

Segmentation Approaches

Physical segmentation:

• Completely separate network infrastructure
• Different switches, routers, firewalls
• Most secure but most expensive

Logical segmentation:

• VLANs with inter-VLAN firewall rules
• Network access control lists
• More flexible, requires careful configuration

Cloud segmentation:

• Separate VPCs or projects
• Security groups and network ACLs
• Native cloud provider controls

Effective Segmentation Requirements

For segmentation to reduce scope, it must:

Segmentation Testing (Requirement 11.4.5)

You must test segmentation controls:

• Every 6 months at minimum
• After any segmentation changes
• As part of annual penetration testing

Testing validates:

• CDE cannot be accessed from out-of-scope segments
• No unexpected network paths exist
• Firewall rules are working as documented

Strategy 3: Outsourcing to Service Providers

Using PCI-compliant service providers shifts compliance responsibilities (and scope) to them.

What Can Be Outsourced

Outsourcing Doesn't Eliminate Responsibility

You remain responsible for:

• Verifying service provider PCI compliance
• Managing the integration correctly
• Documenting the relationship (Requirement 12.8)
• Reviewing compliance status annually

Required documentation:

• Written agreement defining PCI responsibilities
• Service provider's current AOC or compliance certificate
• Understanding of which requirements they cover

Shared Responsibility Models

Example: AWS and PCI DSS

AWS provides the compliant infrastructure; you must secure everything on top of it.

Strategy 4: Point-to-Point Encryption (P2PE)

P2PE encrypts cardholder data at the point of interaction (card reader/terminal) and keeps it encrypted until it reaches the secure decryption environment. Your systems never have access to unencrypted card data.

How P2PE Works

1Card swipe → P2PE terminal encrypts → Your network (encrypted data passes through) → Decryption at processor

Key difference from regular encryption: You cannot decrypt the data. Only the P2PE solution provider can.

P2PE Benefits

P2PE Requirements

To qualify for scope reduction:

• Must use a PCI-validated P2PE solution (check PCI SSC listing)
• Must follow the solution provider's implementation guide
• Cannot store decrypted cardholder data
• Cannot have access to decryption keys

P2PE Limitations

• Only applies to card-present transactions
• Doesn't cover e-commerce
• Must use specific approved devices
• Solution provider costs may be higher

Strategy 5: Hosted Payment Pages and iframes

For e-commerce, using hosted payment forms keeps card data entirely off your servers.

Redirect to Hosted Payment Page

1Customer → Your checkout page → Redirect to Stripe Checkout → Payment processed → Return to your site

Scope impact: SAQ A (simplest)

Advantages:

• Card data never touches your servers
• Payment provider handles PCI compliance for payment page
• Quick implementation

Considerations:

• Customer leaves your site temporarily
• Less control over checkout UX

Embedded iframes

1Customer → Your checkout page (with Stripe Elements iframe) → Card data goes directly to Stripe → Token returned

Scope impact: SAQ A (with proper implementation)

How iframes protect you:

• iframe content controlled by payment provider
• Same-origin policy prevents your JavaScript from accessing card data
• Card data transmitted directly to payment provider

Requirements for SAQ A eligibility:

• iframe hosted by PCI-compliant service provider
• Your page doesn't receive or process card data
• Proper iframe implementation (no JavaScript access)

Client-Side Tokenization (SAQ A-EP)

If you serve the payment page but use JavaScript tokenization:

1Customer → Your checkout page → Stripe.js encrypts and sends to Stripe → Token returned

Scope impact: SAQ A-EP (~191 questions in v4.0)

Why more scope: Your server serves the page containing the payment form, so web server security becomes your responsibility.

Scope Reduction Decision Matrix

Choose your approach based on your business needs:

Implementing Scope Reduction

Step 1: Document Current State

• Map all cardholder data flows
• Identify all systems in current scope
• Understand current SAQ type
• Document current compliance costs

Step 2: Evaluate Reduction Options

• Which strategies apply to your business model?
• What's the implementation cost vs compliance cost reduction?
• Are there business requirements that prevent certain approaches?
• What's the risk profile of each option?

Step 3: Plan Implementation

• Prioritize changes by impact and effort
• Create detailed implementation timeline
• Plan for testing and validation
• Document new architecture

Step 4: Implement and Test

• Implement changes in phases if possible
• Test segmentation controls
• Validate new data flows
• Confirm SAQ type with QSA or acquirer

Step 5: Update Documentation

• Update network diagrams
• Revise data flow documentation
• Update policies and procedures
• Complete new SAQ type

Common Scope Reduction Mistakes

Mistake 1: Incomplete Segmentation

Problem: Firewall rules allow some unnecessary traffic between CDE and corporate network.

Impact: Corporate network remains in scope.

Solution: Audit all firewall rules, implement deny-all default, document every allowed connection.

Mistake 2: Forgetting Connected Systems

Problem: Backup server backs up CDE systems and connects to corporate network.

Impact: Backup server and its connected systems are in scope.

Solution: Segment backup infrastructure or use encrypted, tokenized backups.

Mistake 3: Misunderstanding Tokenization

Problem: Thinking tokens eliminate all compliance requirements.

Impact: Failing to implement required controls for token handling.

Solution: Understand that tokenization reduces but doesn't eliminate scope; complete appropriate SAQ.

Mistake 4: Not Testing Segmentation

Problem: Assuming network segmentation works without testing.

Impact: Failed QSA assessment, potential breach exposure.

Solution: Test segmentation every 6 months per Requirement 11.4.5.

Mistake 5: Improper iframe Implementation

Problem: JavaScript on parent page can access iframe content.

Impact: May not qualify for SAQ A.

Solution: Ensure proper cross-origin isolation, verify implementation with payment provider.

Frequently Asked Questions

If I use Stripe, do I have any PCI scope?

Yes, but it's minimal. You still need to complete SAQ A and maintain basic controls for how you integrate with Stripe. You're responsible for not introducing vulnerabilities in your integration.

Can I reduce scope mid-year?

Yes. You can implement scope reduction at any time. Your next assessment will cover the reduced scope. Document the change and update your compliance approach.

Does using AWS reduce my PCI scope?

AWS helps by providing compliant infrastructure, but you're still responsible for everything you build on it. You inherit their physical security controls but must implement your own application and data security.

How do I know if my segmentation is effective?

Test it. Hire a penetration tester to verify they cannot reach CDE systems from out-of-scope networks. Document the testing and results.

Need help evaluating scope reduction strategies for your environment? Talk to our team

Sources

• PCI DSS Scoping and Segmentation Guidance - Official PCI SSC guidance
• PCI SSC Tokenization Guidelines - Tokenization guidance
• PCI P2PE Solution Requirements - P2PE program documentation