What is Public Key Infrastructure (PKI)?
Public Key Infrastructure (PKI) is a framework of technologies, policies, and procedures that enables secure electronic communications. At its core, PKI provides the foundation for:
- Encryption: Protecting data in transit and at rest
- Authentication: Verifying the identity of users and systems
- Integrity: Ensuring data hasn't been tampered with
- Non-repudiation: Proving the origin of digital communications
Why PKI Matters for Enterprise Security
In today's digital enterprise, PKI is fundamental to:
- Securing web applications with HTTPS
- Authenticating users and devices
- Signing code and documents
- Enabling secure email communication
- Supporting zero-trust architectures
Core PKI Components
Certificate Authority (CA)
The Certificate Authority is the trusted entity that issues digital certificates. CAs can be:
- Public CAs: Trusted by browsers (DigiCert, Let's Encrypt, Sectigo)
- Private/Internal CAs: Operated by organizations for internal use
- Intermediate CAs: Subordinate CAs that issue end-entity certificates
Digital Certificates
Certificates are electronic documents that bind a public key to an identity. Key certificate types include:
- TLS/SSL Certificates: Secure web communications
- Code Signing Certificates: Verify software authenticity
- Email Certificates (S/MIME): Encrypt and sign emails
- Client Certificates: Authenticate users and devices
- Device Certificates: Identify IoT and machine identities
Public and Private Keys
PKI uses asymmetric cryptography with key pairs:
- Public Key: Shared openly, used for encryption and verification
- Private Key: Kept secret, used for decryption and signing
Certificate Revocation
Mechanisms to invalidate certificates before expiration:
- CRL (Certificate Revocation List): Periodic list of revoked certificates
- OCSP (Online Certificate Status Protocol): Real-time revocation checking
- OCSP Stapling: Efficient revocation status delivery
How PKI Works
Certificate Issuance Process
- Key Generation: Entity generates public/private key pair
- CSR Creation: Certificate Signing Request includes public key and identity
- Validation: CA verifies the identity of the requester
- Issuance: CA signs the certificate with its private key
- Distribution: Certificate is delivered to the requester
- Installation: Certificate is deployed to servers/applications
Certificate Validation
When establishing a TLS connection:
- Server presents its certificate
- Client verifies certificate signature chain
- Client checks certificate validity dates
- Client verifies certificate is not revoked
- Client confirms certificate matches the domain
- Secure connection is established
Enterprise PKI Management
Building an Internal PKI
For enterprise PKI management, organizations typically implement:
Root CA
- Offline, air-gapped for maximum security
- Long-lived certificate (10-20 years)
- Minimal direct certificate issuance
Issuing/Intermediate CAs
- Online for certificate issuance
- Medium-lived certificates (3-5 years)
- Separate CAs for different purposes
Registration Authority (RA)
- Validates certificate requests
- Enforces organizational policies
- May be integrated with identity systems
PKI Policy Framework
Effective enterprise PKI requires documented policies:
- Certificate Policy (CP): What certificates can be used for
- Certification Practice Statement (CPS): How the CA operates
- Key Management Policy: How keys are generated and stored
- Certificate Lifecycle Policy: Validity periods and renewal procedures
PKI for Modern Infrastructure
Cloud-Native PKI
Modern cloud environments require:
- Automated certificate provisioning
- Short-lived certificates (hours/days vs. years)
- Dynamic scaling of certificate infrastructure
- Multi-cloud certificate management
Zero Trust and PKI
PKI enables zero trust architectures through:
- Strong identity verification
- Mutual TLS (mTLS) between services
- Device certificate authentication
- Continuous certificate validation
Machine Identity Management
Beyond user certificates, enterprises must manage:
- Service account certificates
- Container and pod identities
- IoT device certificates
- API client certificates
Common PKI Challenges
Certificate Sprawl
Organizations often struggle with:
- Unknown certificates across infrastructure
- Shadow IT certificate deployments
- Orphaned certificates without owners
- Inconsistent certificate management practices
Key Management
Secure key handling requires:
- Hardware Security Modules (HSMs) for sensitive keys
- Proper key backup and recovery procedures
- Key rotation policies
- Secure key storage for all environments
Compliance
PKI operations must meet regulatory requirements:
- PCI DSS for payment systems
- HIPAA for healthcare
- SOC 2 for service organizations
- Industry-specific standards
Getting Started with Enterprise PKI
Assessment
Begin by understanding your current state:
- Inventory existing certificates
- Identify certificate authorities in use
- Document current management processes
- Assess compliance requirements
Strategy Development
Create a comprehensive PKI strategy:
- Define certificate policies
- Design CA hierarchy
- Select PKI management tools
- Plan for automation
Implementation
Roll out enterprise PKI capabilities:
- Deploy certificate management platform
- Configure discovery and monitoring
- Implement automation workflows
- Train teams on new processes
Conclusion
Public Key Infrastructure is the foundation of modern enterprise security. Understanding PKI fundamentals is essential for security professionals, developers, and IT operations teams. With proper enterprise PKI management, organizations can secure their digital communications, enable zero trust architectures, and maintain compliance with regulatory requirements.
TigerTrust provides comprehensive enterprise PKI management capabilities, from internal CA operations to certificate lifecycle automation, helping organizations build and maintain a secure PKI infrastructure.