PKI in practice: Use cases, challenges, and trade-offs

Use cases for PKI

PKI is now most commonly associated with securing websites via TLS/SSL, but its origins are broader, focused on enabling secure communication and verifying identities across digital systems. Today, its applications extend across multiple areas:

• IoT and OT devices: PKI enables secure device authentication and encrypted communication. Only authorised devices can connect to critical systems, reducing the risk of breaches or service disruptions.
• TLS/SSL encryption: Protects web traffic, ensuring data in transit cannot be intercepted or tampered with.
• Email security (S/MIME): PKI allows encrypted and signed emails, ensuring confidentiality and proving sender authenticity.
• Code signing: Verifies software integrity and origin, preventing tampering or malicious distribution.
• Internal services and applications: PKI authenticates users and systems within an enterprise, maintaining secure access to sensitive resources.

By supporting these scenarios, PKI provides a scalable and flexible approach to digital trust.

Challenges in implementing PKI

While PKI is a powerful tool for securing networks and digital interactions, its implementation comes with several operational and technical challenges. Building and managing a Certificate Authority (CA), establishing trust chains, and maintaining verification processes all require specialised expertise. Errors at any stage can undermine the security of the entire system.

Effective certificate lifecycle management is also critical: certificates must be issued, renewed, and revoked systematically, as failing to do so can lead to service outages or security gaps.

Protecting private keys is another essential consideration, since compromised keys can invalidate trust across all connected systems. Organisations typically use Hardware Security Modules (HSMs) and secure backups to safeguard these keys.

Finally, scalability can be a challenge, particularly in large IoT deployments or distributed networks, where automated PKI management is necessary to maintain trust across thousands of devices and services.

Trade-offs to consider

Organisations must weigh several factors when choosing a PKI strategy:

• Public vs private PKI: Public PKI provides broad trust via well-known certificate authorities, while private PKI offers more control but requires more operational effort.
• PKI vs pre-shared keys (PPSK): Pre-shared keys are easier to deploy but less secure, particularly in dynamic or untrusted environments. PKI offers scalability and stronger trust mechanisms.
• Hosted/managed vs in-house PKI:Managed PKI services reduce operational overhead, whereas in-house PKI gives full control but increases complexity and risk.

Choosing the right balance depends on the organisation’s risk tolerance, scale, and IT resources.

Four best practices for PKI adoption

To make PKI effective, we have four best practices for organisations that want to adopt it.

1. Automate certificate lifecycle management: Reduce errors and service disruptions by automating issuance, renewal, and revocation.
2. Use HSMs for private key security: Protect critical cryptographic assets and ensure recovery options.
3. Implement certificate policies: Define clear rules for certificate issuance, usage, and validation.
4. Regular monitoring and validation: Continuously check certificate status and validity to prevent misuse or accidental expiration.

These measures ensure PKI delivers both security and operational efficiency.

Next steps

PKI is more than a technical solution; it’s the backbone of digital trust for modern enterprises. By understanding its use cases, acknowledging its challenges, and applying best practices, organisations can secure devices, applications, and data across increasingly complex networks.

If you’re ready to take the next step, get in touch with our team to discuss how Nomios can help strengthen your digital identity and simplify certificate management.