DNS Record Validation

Alternative Authentication Method for CTN

Overview

DNS Record Validation provides a lightweight, low-assurance alternative to traditional business registry verification (LEI, KvK) for organization authentication in the Connected Trade Network. This method leverages existing DNS infrastructure to enable organizations to demonstrate domain control with minimal administrative overhead.

Motivation

While legal registry-based verification provides strong assurance, it can be resource-intensive and may not be available for all organizations. DNS validation offers:

• Low Friction: Requires only DNS record access
• Automation-Friendly: Machine-verifiable with minimal manual oversight
• Industry Precedent: Already used in SSL/TLS (ACME), email auth (SPF/DKIM/DMARC)
• Quick Bootstrap: Enables rapid onboarding for pilot programs

Method

Challenge Mechanism

1. Association Register generates unique validation token for organization
2. Organization publishes token in DNS under reserved namespace
3. Association Register verifies DNS record via standard resolution

Record Format

_ctn-register.example.org.  IN  TXT  "ctn-validation-token-12345"

Alternative CNAME approach for delegated validation:

_ctn-register.example.org.  IN  CNAME  _validated.ctn.network.

Verification Process

sequenceDiagram
    participant Org as Organization
    participant ASR as Association Register
    participant DNS as DNS System
    
    Org->>ASR: Request DNS validation
    ASR->>ASR: Generate unique token
    ASR-->>Org: Return token & instructions
    
    Org->>DNS: Create TXT record
    Note over DNS: _ctn-register.example.org<br/>TXT "ctn-validation-token-12345"
    
    Org->>ASR: Request verification
    ASR->>DNS: Query TXT record
    DNS-->>ASR: Return token
    ASR->>ASR: Validate token match
    
    alt Token matches
        ASR-->>Org: Validation successful
        ASR->>ASR: Mark as DNS-validated
    else Token mismatch
        ASR-->>Org: Validation failed
    end

Implementation Details

Token Generation

• Use cryptographically secure random generator
• Minimum 128 bits of entropy
• Base64url encoding for DNS compatibility
• Include timestamp for expiration tracking

Validation Logic

def validate_dns_record(domain: str, expected_token: str) -> bool:
    """Validate DNS TXT record for domain ownership."""
    try:
        # Query DNS for TXT records
        records = dns.resolver.query(f"_ctn-register.{domain}", "TXT")

        # Check each TXT record for token
        for record in records:
            if expected_token in str(record):
                return True

        return False
    except dns.resolver.NXDOMAIN:
        return False

Refresh Requirements

• Initial validation: Valid for 90 days
• Renewal validation: Valid for 365 days
• Automated monitoring for record removal
• Grace period of 7 days for DNS issues

Security Considerations

Assurance Level

• Classification: LOW ASSURANCE
• Capability: Proves domain control only
• Limitation: Does not verify legal entity identity
• Risk: Temporary domain hijacking could enable impersonation

Threat Mitigation

Threat	Mitigation
DNS Cache Poisoning	DNSSEC validation required
Subdomain Takeover	Validate apex domain only
Token Reuse	Time-limited, single-use tokens
Social Engineering	Clear labeling as low-assurance

Policy Integration

Organizations validated via DNS receive restricted VAD claims:

{
  "https://schemas.ctn.network/claims/validation/method": "DNS",
  "https://schemas.ctn.network/claims/validation/assurance_level": "LOW",
  "https://schemas.ctn.network/claims/validation/domain": "example.org",
  "https://schemas.ctn.network/claims/validation/validated_at": "2025-01-15T10:00:00Z"
}

Comparison with Other Methods

Method	Assurance	Complexity	Time	Cost	Use Case
DNS Validation	Low	Low	Minutes	Free	Quick onboarding, pilots
KvK Registry	High	Medium	Days	€€	Dutch companies
LEI Registration	High	High	Weeks	€€€	International corps
EORI Verification	High	Medium	Days	€€	EU traders
eHerkenning (EH3/EH4)	High	Medium	Minutes–Days	€€	Dutch entities; optional, see below
Manual Review	Variable	High	Weeks	€€€€	Special cases

eHerkenning Authentication (optional)

Optional. eHerkenning is not part of the 2026 baseline and is not required for any participant. It applies to Dutch entities only.

eHerkenning (EH3/EH4) is the Dutch government’s authorised-representation scheme. In CTN it is used as a step-up verification of organisational representation (a KvK cross-check), not as a domain-validation method and not as a login. The verification flow, evidence format, and security guardrails are described in Member Onboarding §3.6. It ranks as a HIGH-assurance identity verification alongside KvK and LEI; the resulting EHerkenning verification contributes to the participant’s trust level, which a data provider may consult when applying its local authorisation policy.

Implementation Phases

Phase 1: Pilot (Current)

• Manual token generation
• Email-based instructions
• Manual verification trigger
• Limited to pilot participants

Phase 2: Automated (Q2 2025)

• Self-service portal
• Automated verification
• API integration
• Monitoring dashboard

Phase 3: Enhanced (Q3 2025)

• Multi-domain validation
• Subdomain delegation
• DNSSEC enforcement
• CAA record integration

Configuration

Association Register Settings

dns_validation:
  enabled: true
  namespace: "_ctn-register"
  token_length: 32
  token_charset: "alphanumeric"
  ttl_initial: 7776000  # 90 days
  ttl_renewal: 31536000  # 365 days
  grace_period: 604800  # 7 days
  dnssec_required: false  # Phase 3
  allowed_record_types:
    - TXT
    - CNAME

Access Restrictions

Organizations validated via DNS:

• Cannot access high-sensitivity data
• Limited to read-only operations initially
• Require additional verification for write access
• Must transition to higher assurance within 12 months

References

• RFC 8555: Automatic Certificate Management Environment (ACME)
• RFC 7208: Sender Policy Framework (SPF)
• RFC 6376: DomainKeys Identified Mail (DKIM)
• RFC 7489: Domain-based Message Authentication (DMARC)
• RFC 8659: DNS Certification Authority Authorization (CAA)

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