What Is PKIaaS? PKI as a Service for Machine Identity Security

Public Key Infrastructure (PKI) is no longer a niche security function buried inside IT, it has truly become foundational infrastructure. Today, PKI is essential for enterprise security, enabling machine identity, encrypted communications, Zero Trust architectures, and regulatory compliance across cloud, hybrid, and on-prem environments.

As certificate lifecycles shorten, cryptographic risk increases, and environments become more distributed, many organizations are re-evaluating whether traditional, on-premises PKI can keep up. This has led many organizations to explore adopting PKIaaS (PKI as a Service). 

This guide explains what PKIaaS is, how it compares to on-prem PKI, the advantages and challenges of adopting PKIaaS, and how organizations can successfully migrate from legacy PKI to a modern, automated PKIaaS model, all without disrupting critical systems.

What is PKIaaS (PKI as a Service)?

PKIaaS (Public Key Infrastructure as a Service) is a cloud-delivered model for providing core PKI capabilities, including certificate authorities (CAs), key management, certificate issuance, lifecycle automation, and cryptographic policy enforcement, as a managed service.

Rather than deploying, operating, and scaling PKI infrastructure internally, organizations consume PKI as a service that is highly available, automation-ready, and designed for hybrid and cloud-native environments. PKIaaS abstracts the underlying PKI control plane while exposing PKI functionality through secure APIs, integrations, and policy-driven workflows.

Core PKI Capabilities Delivered via PKIaaS

A modernized PKIaaS platform provides a broad range of machine identity security capabilities including:

• Private and public certificate authorities, including root and issuing CAs, with defined trust hierarchies
• Key generation, storage, and protection, often backed by FIPS 140-2 or 140-3 compliant hardware security modules (HSMs)
• Certificate issuance and validation for TLS, mTLS, client authentication, code signing, and workload identities
• Full certificate lifecycle management, including automated renewal, rotation, revocation, and expiration handling
• Cryptographic policy enforcement across algorithms, key sizes, certificate lifetimes, and usage constraints

These services are delivered with built-in redundancy, SLAs, and monitoring. This reduces the operational and security risks traditionally associated with self-managed PKI.

Designed for Automation, Scale, and Modern Workloads

Leading PKIaaS platforms are architected to support the scale and dynamism of modern environments, including public cloud, Kubernetes, CI/CD pipelines, and distributed applications. An API-first design enables:

• Automated certificate issuance and renewal as part of deployment workflows
• Support for short-lived certificates and just-in-time trust
• Integration with load balancers, ingress controllers, service meshes, and secrets managers
• Consistent trust enforcement across hybrid and multi-cloud environments

By shifting PKI from resource-intensive infrastructure to an operational service, PKIaaS allows security teams to focus on policy, automation, and risk management rather than CA maintenance. By migrating to PKIaaS, many organizations find that PKI becomes a more easily programmable and resilient foundation for machine identity security and Zero Trust architectures.

PKIaaS vs. On-Premise PKI

The difference between PKIaaS and traditional on-premise PKI is not simply where certificate authorities are hosted. It reflects a broader shift in how organizations design, operate, and scale cryptographic trust.

Traditionally, on-premise PKI models were built for static, internal environments with predictable certificate volumes and long-lived credentials. In recent years, the PKI landscape has shifted significantly, driven by major forthcoming changes in certificate lifecycles, algorithms and compliance requirements. PKIaaS is more adaptable to the modern reality of dynamic, distributed, and automation-driven environments where certificate issuance and rotation are continuous.

PKIaaS vs On-Premise PKI: Technical Comparison

In an on-premise PKI deployment, organizations are responsible for the full PKI stack, including CA hierarchy design, HSM lifecycle management, OS patching, backup and recovery, and availability engineering.

PKIaaS frees the organization from many of these responsibilities, moving them into the hands of the cloud PKI providers.  The service provider operates the CA infrastructure, cryptographic enforcement mechanisms, and availability layers, while customers interact with PKI through APIs, integrations, and policy-driven workflows. This model empowers security teams to focus their efforts on higher value activities such as trust architecture and lifecycle governance, rather than tedious day-to-day PKI infrastructure and maintenance.

An important note is that many enterprises now use a “Hybrid PKI” where the Root CA is kept offline/on-premise for maximum sovereignty, while the Issuing CAs are hosted in the cloud (PKIaaS) for speed and API access.

The Key Driver of the PKIaaS Push

Many organizations running legacy PKI models are coming to terms with the reality that on-premise PKI environments often struggle to keep pace with:

• Rapid certificate growth
• Shortening certificate lifetimes
• Ephemeral workloads and CI/CD pipelines
• Multi-cloud and hybrid trust requirements

Conversely, PKIaaS platforms are purpose-built for these realities, enabling automated certificate issuance, renewal, and revocation across modern workloads while reducing operational risk and dependency on specialized internal PKI expertise.

Advantages of PKIaaS

While the architectural shift from on-premise PKI to PKIaaS can be significant, there are substantial operational, security, and strategic benefits from the transition.

Improved Operational Resilience and Availability

PKIaaS platforms are typically engineered with built-in redundancy across multiple availability zones or regions. This significantly reduces the risk of outages caused by:

• CA service failures
• CRL or OCSP responder unavailability
• Infrastructure maintenance windows
• Human error during patching or upgrades

For many organizations, PKI availability is a hidden single point of failure. By design, PKIaaS significantly reduces the risk of costly outages and failures.

Support for Short-Lived Certificates and Automation

As certificate lifetimes continue to shrink, including the move toward 47-day TLS certificates, manual renewal processes no longer scale. PKIaaS enables:

• High-frequency issuance and renewal
• Just-in-time certificate provisioning
• Automated rotation aligned with DevOps pipelines
• Reduced blast radius when keys are compromised

This is particularly important for machine identities, where certificates may be issued and rotated daily or even hourly.

Reduced Cryptographic and Compliance Risk

PKIaaS platforms enforce consistent cryptographic policies across the environment, helping organizations:

• Standardize algorithms and key sizes
• Enforce certificate lifetime policies
• Align with evolving compliance and regulatory requirements
• Promote crypto agility with enhanced readiness for future cryptographic transitions, including adopting quantum resistant algorithms

Instead of relying on tribal knowledge, governance becomes codified and enforceable under a PKIaaS model.

Faster Time to Value

Standing up a production-ready PKI environment on-premise can take months. PKIaaS significantly accelerates deployment, allowing organizations to:

• Onboard new workloads faster
• Enable secure communications earlier in application lifecycles
• Reduce delays caused by PKI infrastructure dependencies

For some organizations, a full migration to PKIaaS is not viable due to security and compliance requirements. In those cases, a hybrid model can provide many of the benefits of PKIaaS while still ensuring the root CA or keys are kept securely on premises.

How to Migrate from Legacy PKI to PKIaaS

Migrating PKI is a high-risk activity if not done correctly. Certificates are deeply embedded into applications, infrastructure, and trust relationships. A successful migration requires a structured, phased approach. Here is a brief outline of Accutive Security’s approach to migrating organizations to PKIaaS.

Phase 1: PKI Discovery and Assessment

Before any migration begins, complete visibility into the existing environment is required. The team establishes a “source of truth” by identifying:

• Existing Trust Chains: Mapping every root and intermediate CA.
• Certificate Inventory: Identifying active certificates, their use cases, and expiration dates.
• Hidden Dependencies: Uncovering unmanaged “shadow” certificates and renewal processes that exist only in undocumented scripts or individual knowledge.

Phase 2: PKI Architecture and Trust Model Design

To minimize risk, PKI experts generally advise against a “Big Bang” cutover. Instead, this phase defines:

• Workload Prioritization: Selecting high-value or low-risk use cases to move first (e.g., DevOps workloads or internal TLS).
• Hybrid Coexistence: Designing an architecture where legacy and PKIaaS environments work in parallel, ensuring that new trust roots are distributed without breaking existing connections.
• Policy Alignment: Updating Certificate Practice Statements (CPS) to reflect the new cloud-delivered model.

Phase 3: Controlled Certificate Issuance from PKIaaS

Rather than attempting to “move” existing certificates, which can jeopardize private key security, this phase typically focuses on transition through attrition:

• New Issuance: All new requests are routed through the PKIaaS platform.
• Incremental Replacement: Legacy certificates are replaced naturally as they hit their expiration window.
• Validation: Continuous monitoring of application behavior as the environment shifts toward the new authority.

Phase 4: Expansion and Optimization

Once the foundation is proven, the focus shifts from “migration” to “modernization.” This phase maximizes the ROI of your new infrastructure:

• Agile Automation: Integrating PKIaaS with CI/CD pipelines, Kubernetes (via cert-manager), and MDM solutions to remove manual touchpoints.
• Identity-First Security: Safely reducing certificate lifetimes from years to days—or even hours—to drastically shrink the window of vulnerability.
• Strategic Oversight: Many organizations find that while PKIaaS removes the hardware burden, the policy and compliance requirements remain complex.

To ensure long-term health, organizations often leverage Managed PKI Services. Partnering with PKI experts empowers your internal teams to focus on core innovation while a dedicated PKI team handle the 24/7 operational vigilance, policy enforcement, and complex integrations that keep a modern PKI environment secure.

Phase 5: Decommissioning Legacy PKI

Unfortunately, most PKIaaS vendors will not decommission your legacy on-premise PKI. For many organizations, the legacy PKI often remains in place longer than necessary due to fear of outages or unknown dependencies. The additional costs and resource drain of running two systems in parallel longer than necessary limits the ROI of too many PKIaaS projects. Accutive Security views decommissioning as a deliberate and auditable Phase 5 of the PKIaaS migration process.

The key steps that we undertake include:

• Verifying that no active certificates depend on legacy CAs
• Allowing sufficient overlap for trust chain validation
• Revoking and retiring unused CAs
• Documenting the process for audit and compliance

By decommissioning legacy PKI as soon as it is safe to do so, organizations reduce operational costs, the attack surface, and the cryptographic risk to the organization.

PKI Maturity Model (PKIMM) and PKIaaS as an Accelerant

To build a resilient security posture, organizations must move beyond simply “having a CA” to achieving measurable maturity. As a member of the PKI Consortium, Accutive Security leverages the proven PKI Maturity Model (PKIMM) as a standardized framework to evaluate organization’s progress across five distinct levels:

1. Initial – Processes are ad-hoc, unpredictable, and purely reactive. There is no central inventory, and knowledge is often siloed within a single individual.
2. Basic – Defined processes exist for specific projects, but they are not aligned with industry standards (CP/CPS). Controls remain reactive and inconsistent.
3. Advanced – Standards are established and proactive. Organizational standards for certificate services are defined, though consistency across all departments may still vary.
4. Managed – PKI is consistently managed, measured, and controlled. A proactive approach is taken toward certificate and key management, supported by well-defined policies and skilled resources.
5. Optimized – The peak of digital trust. Processes undergo continuous improvement, and the infrastructure is “future-proof,” adapting proactively to new technology and regulatory changes.

PKIaaS: The Catalyst for Maturity

While maturity is defined by People, Process, and Technology, PKIaaS is a primary enabler for organizations that reach Levels 4 and 5. It directly addresses the four modules of the PKIMM:

• Management & Operations: PKIaaS replaces manually maintained servers with elastic, API-first infrastructure, enabling the Automation and Resilience required for Level 4.
• Governance: By centralizing the CA in a managed cloud environment, organizations can more easily enforce a unified Certificate Policy (CP) across the entire enterprise.
• Resources: PKIaaS solves the “Knowledge Gap” (a common Level 1-2 risk) by offloading the burden of specialized infrastructure maintenance to experts.

Moving Beyond the Tool

The objective is not merely to host a PKI in the cloud, but to achieve Optimized (Level 5) cryptographic trust. This requires a transition from manual issuance to automated lifecycle management (CLM) integrated into Zero Trust and DevSecOps workflows.

PKIaaS Security Model & Shared Responsibility

Transitioning to PKIaaS does not mean a total hand-off of security responsibilities. Instead, it shifts the focus from physical and infrastructure security to logical and policy-based security. To successfully reach the Managed (Level 4) or Optimized (Level 5) stages of the PKIMM, organizations must understand where the provider’s duties end and the customer’s begin.

The PKIaaS security model is built on a “Shared Responsibility” framework, similar to other cloud services (SaaS/PaaS).

Common PKIaaS Challenges (and How to Avoid Them)

While PKIaaS delivers substantial benefits, organizations often underestimate the complexity involved in implementing and operating PKI correctly in a cloud-delivered model. Understanding these challenges upfront is critical to realizing the full value of PKIaaS. Here are some of the common challenges or pitfalls encountered during and after PKIaaS implementation:

Treating PKIaaS as a “Lift-and-Shift” Infrastructure Project

PKIaaS is not simply on-prem PKI hosted elsewhere. Organizations that attempt to replicate legacy certificate practices in the cloud often carry forward:

• Overly long certificate lifetimes
• Manual approval workflows
• Inconsistent certificate profiles
• Weak ownership and accountability models

To succeed, PKIaaS adoption must be paired with modernization of policies, lifecycles, and automation strategies.

Lack of Certificate Lifecycle Visibility

PKIaaS platforms provide issuance and cryptographic services, but they do not automatically solve visibility challenges. Without integrated Certificate Lifecycle Management (CLM), organizations may still struggle with:

• Unknown certificate ownership
• Expiration risk
• Shadow certificates issued outside policy

PKIaaS and CLM must be implemented together to avoid recreating legacy problems in a new platform.

Fragmented Ownership Across Teams

PKI often spans security, infrastructure, DevOps, networking, and application teams. Without clear ownership and governance, PKIaaS initiatives can stall due to:

• Conflicting requirements
• Inconsistent policy enforcement
• Manual exceptions that undermine automation

Successful PKIaaS programs establish centralized governance with clearly defined responsibilities across teams.

Over-Reliance on Platform Defaults

PKIaaS platforms are powerful, but default configurations rarely align perfectly with enterprise risk, compliance, or audit requirements. Certificate profiles, key sizes, lifetimes, and revocation behaviors must be intentionally designed—not assumed.

PKIaaS Solution Evaluation and Selection

Not all PKIaaS offerings are created equal. As organizations strive to elevate their PKI maturity, it is important to evaluate platforms against both current technical capabilities and the ability to adapt to future cryptographic shifts. The PKIaaS solution evaluation criteria should be tailored to your organization’s operational, security and compliance requirements; however, here is a frequent baseline evaluation criteria:

Cryptographic Sovereignty and HSM Integration

The PKIaaS platform is the orchestration layer, but the Root of Trust lives in the HSM. Evaluation should focus on how the service supports and secures that hardware layer:

• FIPS 140-3 Support: Does the PKIaaS platform support integration with FIPS 140-2 Level 3 or 140-3 HSMs? This is the industry benchmark for high-assurance environments.
• Key Ownership Models: Does the provider offer dedicated HSM support? You should evaluate whether the platform allows for “Bring Your Own HSM” (BYOK) or if it provides logically isolated partitions that ensure the service provider never has clear-text access to your private keys.
• PQC Readiness: Mature PKI platforms are “crypto-agile.” Ensure that the selected PKIaaS platform has a roadmap for Post-Quantum Cryptography (PQC) and can support quantum-resistant algorithms.

Seamless Integration & Automation (The CLM Factor)

It is important to pair  CA that cannot communicate with your existing stack is a liability.

• Native Ecosystems: Look for out-of-the-box support for tools and platforms you utilize (e.g. Kubernetes, HashiCorp Vault, and major MDM providers (Intune/Jamf).
• Standardized Protocols: Robust support for ACME, SCEP, and EST is essential for moving away from manual, ticket-based issuance.
• API-First Architecture: The platform should offer a comprehensive REST API that allows PKI to be treated as “Infrastructure as Code.”

Operational Resilience & Transparency

Availability is the most critical metric for PKI; if your CA or CRL goes offline, your entire authentication fabric can collapse.

• Global Footprint: Evaluate multi-region, multi-cloud redundancy to ensure the CRL and OCSP responders are globally distributed and low-latency.
• Auditability: Does the platform provide real-time, tamper-evident logs for all issuance and administrative actions? This is a prerequisite for Managed (Level 4) PKI maturity.

Governance, Policy, and CPS Enforcement

PKIaaS simplifies infrastructure, but governance remains an enterprise responsibility. A mature PKIaaS platform must enable centralized, enforceable policy rather than relying on informal processes or tribal knowledge.

Key governance evaluation criteria include:

• Certificate Policy (CP) and CPS Alignment: The ability to define, enforce, and audit certificate policies consistently across all issuing authorities.
• Separation of Duties: Support for role-based access controls that separate policy definition, certificate issuance, and audit responsibilities.
• Policy Consistency at Scale: Assurance that cryptographic standards, certificate profiles, and lifetimes are enforced uniformly across teams and environments.
• Audit and Compliance Readiness: Built-in reporting and logging to support regulatory, internal audit, and third-party assessments.

Hybrid PKI and Migration Support

Few enterprises adopt PKIaaS as a clean-slate deployment. Most will operate in a hybrid PKI model for an extended period of time, often retaining on-prem Root CAs while transitioning Issuing CAs to the cloud.

PKIaaS platforms should be evaluated on their ability to support this reality, including:

• Hybrid Trust Architectures: Native support for offline or on-prem Root CAs with cloud-hosted Issuing CAs
• Legacy PKI Coexistence: Compatibility with existing on-prem PKI solutions during phased migrations.
• Incremental Migration Paths: The ability to onboard workloads gradually without breaking existing trust relationships.
• Trust Chain Distribution: Safe and controlled distribution of new trust anchors across diverse environments.

The PKI Expert Gap: Platform vs. Program

The most common mistake organizations make is assuming that purchasing a PKIaaS tool automatically grants them PKI maturity. As outlined in the PKIMM, the Resources module is often the hardest to satisfy. Even the most advanced platform requires an expert to define the Certificate Policy (CP), manage the trust hierarchy, and ensure integrations remain secure.

Most organizations must decide:

• Internal Management: Do we have the specialized cryptographic engineers to manage this 24/7/365?
• Managed Partnership: Should we leverage an experienced partner to reach Level 5 faster?

How PKI Experts Close the Gap

Selecting the right tool is only half the battle. Managed Services (MSP) can help ensure that your PKIaaS solution isn’t just a “cloud-hosted CA,” but a fully governed, automated, and compliant Identity Security Program. PKI experts, such as Accutive Security, provide the specialized human intelligence, the Resources module of the PKIMM, that allows your organization to reach an Optimized state without the overhead of hiring and training dedicated PKI engineers.