Why AWS Private CA?
AWS Private Certificate Authority (PCA) enables organizations to build private PKI infrastructure without the complexity of managing on-premises CA servers. Use cases include:
- Internal TLS: Secure internal service communication
- Mutual TLS (mTLS): Client certificate authentication
- IoT Devices: Device identity and authentication
- Code Signing: Internal software signing
- Document Signing: Internal document workflows
AWS Private CA Architecture
Build a hierarchical PKI with:
- Root CA (offline, highest security)
- Issuing CAs per environment or use case
- End entity certificates for servers, clients, and devices
Creating a Private CA
Root CA Setup
Create a root CA with strong key algorithm (RSA 4096 or ECDSA P384), signing algorithm (SHA512WITHRSA), and appropriate subject fields.
Issuing CA Setup
Create subordinate/issuing CAs signed by the root CA for operational certificate issuance.
Certificate Templates
AWS PCA supports various certificate templates:
| Template | Use Case |
|---|---|
| EndEntityServerAuthCertificate | TLS servers |
| EndEntityClientAuthCertificate | TLS clients |
| CodeSigningCertificate | Code signing |
| SubordinateCACertificate_PathLen0 | Issuing CAs |
| BlankEndEntityCertificate_APIPassthrough | Custom certs |
Issuing Certificates
Via AWS CLI
Issue certificates using acm-pca issue-certificate with CA ARN, CSR, signing algorithm, template ARN, and validity period.
Via TigerTrust
Configure AWS PCA provider with region, CA ARN, template, and auto-renewal policies.
ACM Integration
Certificates can be exported to AWS Certificate Manager with auto-import to regions and services (ELB, CloudFront, API Gateway).
Cross-Account Access
Share your Private CA across AWS accounts using resource-based policies for IssueCertificate and GetCertificate actions.
Use Cases
Kubernetes mTLS
Configure cert-manager with AWS PCA issuer for service mesh certificates.
IoT Device Identity
Issue device certificates with client authentication templates and appropriate validity periods.
Cost Optimization
AWS PCA pricing:
- CA per month: ~$400
- Certificates (first 1000): $0.75 each
- Certificates (1000+): $0.35 each
Cost optimization strategies:
- Consolidate CAs where possible
- Use longer validity periods
- Delete unused CAs
- Consider short-term CA mode
Monitoring
CloudWatch Metrics
Monitor metrics like MisconfiguredCRLDistributionPoints, MisconfiguredOCSP, Success, and Failure rates.
CloudTrail Logging
All AWS PCA API calls are logged to CloudTrail for audit and compliance.
Best Practices
- Use separate CAs for different certificate types - Better security boundaries
- Keep root CA offline - Use only for signing subordinate CAs
- Enable CRL/OCSP - Support certificate revocation
- Implement short validity - 1 year or less for end-entity certificates
- Use IAM policies - Least privilege access to PCA
- Monitor continuously - CloudWatch alerts for failures
Conclusion
AWS Private CA provides a managed, scalable solution for enterprise private PKI. Combined with TigerTrust automation, organizations can build robust internal certificate infrastructure without the operational overhead of traditional CA management.