What is Encryption in Transit

Encryption in transit forms a fundamental security control in third-party risk management. When your vendors handle sensitive data, that information moves across multiple networks—from their applications to yours, between their internal systems, and to their own service providers. Each transmission point creates potential exposure.

Compliance frameworks universally mandate encryption in transit. SOC 2 Type II audits examine TLS configurations. ISO 27001 control A.13.1.1 requires cryptographic protection for network communications. GDPR Article 32 demands "appropriate technical measures" including encryption. PCI DSS Requirement 4 explicitly requires strong cryptography for cardholder data transmission.

For GRC analysts, encryption in transit represents more than a checkbox. You need evidence of implementation, protocol versions, certificate management processes, and incident response procedures for encryption failures. Third-party assessments must verify not just the presence of encryption, but its proper configuration and maintenance.

Technical Implementation Standards

Encryption in transit requires specific cryptographic protocols. Transport Layer Security (TLS) dominates modern implementations, with TLS 1.2 serving as the current minimum standard across compliance frameworks. TLS 1.3 adoption continues growing, offering improved performance and security.

Key protocol requirements:

• Minimum TLS version: 1.2 (1.0 and 1.1 deprecated as of 2020)
• Cipher suites: AES-128 minimum, prefer AES-256
• Key exchange: ECDHE or DHE for perfect forward secrecy
• Authentication: RSA or ECDSA certificates from trusted CAs
• Hash functions: SHA-256 minimum

Regulatory Requirements and Framework Mapping

SOC 2 Trust Services Criteria

CC6.1 requires logical and physical access controls to protect information during transmission. Auditors verify TLS implementation through network scans and configuration reviews. Your vendor's SOC 2 report should detail:

• Encryption protocols used
• Certificate management procedures
• Monitoring for protocol downgrades
• Incident response for certificate issues

ISO 27001:2022 Controls

Control 8.24 (Use of cryptography) mandates documented cryptographic policies. Vendors must demonstrate:

• Cryptographic policy documentation
• Key management procedures
• Regular reviews of encryption effectiveness
• Training for personnel managing certificates

GDPR Compliance

Article 32(1)(a) requires "pseudonymisation and encryption of personal data." Data Protection Authorities interpret this to include transmission encryption. The EDPB guidelines specify TLS as an appropriate measure for controller-to-processor transfers.

PCI DSS 4.0

Requirement 4.1 mandates "strong cryptography and security protocols" for transmitting cardholder data over open, public networks. Specific requirements:

• Document all locations where cardholder data transmitted
• Verify TLS implementation on all transmission points
• Maintain inventory of certificates and expiration dates
• Quarterly vulnerability scans must verify proper TLS configuration

Practical Application in Vendor Assessments

When evaluating third-party encryption in transit, focus on these control points:

1. Data Flow Mapping Request comprehensive data flow diagrams showing:

• All transmission points between systems
• Protocol specifications for each connection
• Certificate authorities used
• Backup communication methods

2. Certificate Management Verify processes for:

• Certificate procurement and validation
• Renewal procedures (automated preferred)
• Revocation capabilities
• Multi-domain and wildcard certificate usage

3. Configuration Standards Review evidence of:

• Disabled legacy protocols (SSL, TLS 1.0/1.1)
• Strong cipher suite selection
• HSTS implementation for web applications
• Certificate pinning for mobile applications

4. Monitoring and Alerting Confirm capabilities for:

• Certificate expiration alerts (30, 14, 7 days)
• Protocol downgrade detection
• Failed handshake monitoring
• Unauthorized certificate usage

Common Implementation Failures

Third-party vendors frequently exhibit these encryption gaps:

Mixed Protocol Environments: Production systems use TLS 1.2 while development or backup systems allow TLS 1.0. Attackers target these weaker endpoints.

Certificate Mismanagement: Expired certificates cause outages. Self-signed certificates in production violate compliance requirements. Wildcard certificates create excessive exposure if compromised.

Incomplete Coverage: Vendors encrypt customer-facing traffic but leave internal API communications unencrypted. East-west traffic between microservices often lacks protection.

Configuration Drift: Initial deployment meets standards, but subsequent changes weaken security. Missing change control processes allow developers to disable encryption for troubleshooting.

Industry-Specific Considerations

Healthcare (HIPAA): The Security Rule §164.312(e)(1) requires encryption for PHI transmission. While HIPAA doesn't specify TLS versions, OCR guidance references NIST standards requiring TLS 1.2 minimum.

Financial Services: SWIFT CSP requires TLS 1.2 for all SWIFT-related communications. Open Banking standards mandate mutual TLS (mTLS) for API authentication.

Government Contractors: NIST SP 800-52 Rev. 2 provides TLS guidelines for federal systems. FedRAMP requires continuous monitoring of encryption controls.

Vendor Evidence Collection

During due diligence, request these artifacts:

1. Network architecture diagrams with encryption points marked
2. Certificate inventory with expiration tracking
3. TLS scan results from the last 90 days
4. Incident reports related to certificate failures
5. Encryption standard operating procedures
6. Training records for certificate management staff

Control Testing Methods

Validate vendor claims through:

• SSL Labs scans for public endpoints
• Nmap scripts to enumerate supported protocols
• Certificate transparency logs to verify CA usage
• Packet captures to confirm encryption during data transfer
• API testing to validate certificate pinning

Frequently Asked Questions

What's the difference between encryption in transit and encryption at rest?

Encryption in transit protects data during movement between systems using protocols like TLS, while encryption at rest protects stored data using methods like AES encryption on databases or file systems. Both are required for comprehensive data protection.

Does using HTTPS automatically mean we have proper encryption in transit?

HTTPS provides encryption but requires proper configuration. Verify TLS version (1.2 minimum), disable weak ciphers, implement HSTS headers, and maintain valid certificates from trusted CAs.

How often should we reassess vendor encryption in transit controls?

Annually at minimum, with continuous monitoring preferred. Trigger immediate reassessment after vendor infrastructure changes, security incidents, or updates to regulatory requirements.

What evidence should vendors provide for SOC 2 compliance?

Vendors should provide TLS configuration screenshots, certificate management procedures, network diagrams showing encryption points, vulnerability scan results confirming strong protocols, and incident response procedures for encryption failures.

Can vendors use self-signed certificates for encryption in transit?

Self-signed certificates provide encryption but fail authentication requirements. Production systems must use certificates from trusted Certificate Authorities. Self-signed certificates may be acceptable only in isolated development environments.

How do we verify encryption for vendor API integrations?

Test API endpoints using tools like OpenSSL or Postman to verify TLS version, examine certificate chains, confirm strong cipher suites, and validate certificate pinning if implemented.