Public vs. Private Certs: What’s the Difference?

Digital certificates play a key role in securing modern IT systems. They are the foundation of Public Key Infrastructure (PKI), making secure communication, authentication, and data integrity possible. However, not all certificates work the same way. IT professionals often need to decide whether to use public or private certificates for their security requirements.

Knowing the difference between these two types is essential for setting up trust models, configuring IT systems, and deploying them correctly. This guide breaks down the key differences, when to use each type, and the best practices for managing public and private certificates.

What Is a Public Certificate?

A public certificate is a digital certificate issued by a trusted, third-party certificate authority (CA), such as DigiCert, GlobalSign, or Let’s Encrypt.

Key Characteristics of Public Certificates

• Globally Recognized Trust: Public certificates are automatically trusted by major browsers, operating systems, and external users. This is because the issuing authorities are already included in the root certificate stores of these platforms.
• Usage: Public certificates are commonly employed for securing websites (via HTTPS), APIs, and other public-facing applications. They ensure external users can establish trusted connections without configuration issues.
• Validation Levels: Public CAs offer different validation options, such as:
  • Domain Validation (DV): Confirms control over a specific domain.
  • Organization Validation (OV): Adds business identity verification.
  • Extended Validation (EV): Provides the highest level of trust and enables visible indicators like the green address bar in browsers.

Common Applications

• Encrypting communications on public websites (e.g., online banking portals).
• Securing email protocols (S/MIME, DKIM, SPF, DMARC).
• Ensuring data integrity in third-party integrations.

Public certificates are ideal when your trust model involves external entities that need immediate verification and compatibility.

What Is a Private Certificate?

A private certificate is issued by an organization’s internal private certificate authority (CA) or enterprise PKI system.

Key Characteristics of Private Certificates

• Restricted Trust Scope: Unlike public certificates, private certificates are not automatically trusted by external entities. They require manual configuration to establish trust within specific environments (e.g., organizational networks).
• Custom Use Cases: These certificates are tailored for internal applications that do not need to interact with broader public networks. They are often used for secure internal communications, device authentication, and private networks.
• Self-Signed Certificates: Private certs can be self-signed, meaning the organization generates and validates them internally without a third-party CA. However, self-signed certificates require careful trust management to avoid security vulnerabilities.

Common Applications

• Authenticating internal corporate systems (e.g., Active Directory services).
• Securing VPNs for remote access.
• Managing internal microservices, Kubernetes clusters, and DevOps workflows.

Private certificates are best suited for controlled, internal environments where trust can be explicitly established and maintained.

When to Use Public vs. Private Certificates

When to Use a Public Certificate

Consider public certificates when the goal is to secure public-facing systems or APIs where trust from external users is critical:

• Websites and e-commerce platforms that require HTTPS encryption.
• Applications that involve external integrations needing publicly trusted certs.
• Email communications to ensure global compatibility and secure delivery.

When to Use a Private Certificate

Private certificates shine in environments where security and control are paramount, but public exposure is unnecessary:

• Corporate intranet applications requiring secure user authentication.
• Device authentication for internal IoT, mobile, or endpoint devices.
• Secure communication between internal application servers and microservices.

Risks of Using the Wrong Type of Certificate

Selecting the wrong type of certificate can lead to significant security and operational risks:

• Using a Private Certificate Publicly: Deploying a private or self-signed certificate on a public-facing website will trigger browser security warnings. These warnings flag the site as untrustworthy, leading to poor user experience and potential financial loss.
• Using a Public Certificate Internally: Public certificates used for internal systems may expose these systems to unnecessary risk if the certificate is leaked or misconfigured. Additionally, the reliance on external CAs can complicate internal processes.

Managing Certificate Lifecycles & Security Best Practices

Effective lifecycle management and adherence to security best practices are essential for minimizing risks. The following strategies can enhance your organization’s certificate management processes:

Automate Certificate Issuance & Renewal

• Use protocols like ACME (Automated Certificate Management Environment) for public certificate automation. ACME streamlines the process of issuing and renewing certs, reducing human error.

Enforce Strong Encryption & Key Management

• Use at least 2048-bit RSA keys or ECDSA P-256 certificates to comply with industry standards.
• Regularly rotate cryptographic keys and certificates to prevent vulnerabilities.
• Avoid using wildcard certificates when possible, as they present a single point of failure.

Monitor & Audit Certificate Usage

• Implement systems that track certificate expiration dates to prevent disruptions.
• Use tools like Certificate Transparency logs and directory insights to review certificate activity and detect unauthorized changes.

Secure Your Organization with JumpCloud

Navigating the complexities of public and private certificates can be daunting, but with the right tools, your organization can streamline the process and prioritize security.

JumpCloud simplifies certificate management by centralizing identity and access controls within a single platform:

• Automate certificate policies and lifecycles.
• Enforce secure authentication practices like MFA and conditional access.
• Monitor and audit activity with Directory Insights.

With JumpCloud, IT teams can ensure secure, frictionless access while maintaining compliance across diverse environments.

Explore More

Try a guided simulation of JumpCloud’s capabilities or contact our sales team to see how we can support your security and certificate management needs.