Intermediate (CA)

An Intermediate Certificate Authority (CA) is a type of Certificate Authority that operates hierarchically below a Root CA in a Public Key Infrastructure (PKI). Intermediate CAs are used to issue and manage digital certificates on behalf of the Root CA, helping to enhance security and manage the certificate issuance process.

Role and Functions of an Intermediate CA:

• Certificate Issuance: Intermediate CAs issue digital certificates to end entities (users, devices, servers) based on the policies and guidelines set by the Root CA.
• Enhanced Security: By placing an Intermediate CA between the Root CA and end-entity CAs, security is increased since the private key of the Root CA is kept offline and isolated.
• Policy Enforcement: Intermediate CAs enforce specific policies and practices defined by the Root CA for certificate issuance and management.
• Revocation Management: Intermediate CAs can handle the revocation of certificates issued by them, improving efficiency and response time.
• Reduced Risk: If an Intermediate CA is compromised, the impact is limited to the certificates issued by that Intermediate CA, reducing the risk to the entire PKI.

Intermediate CA Hierarchy:

In a PKI hierarchy, Intermediate CAs are situated between the Root CA and end-entity CAs. This creates a chain of trust where the Root CA is at the top and Intermediate CAs branch out from it. End-entity CAs issue certificates to individuals, devices, or services.

Benefits of Intermediate CAs:

• Enhanced Security: Protects the private key of the Root CA by limiting its exposure.
• Granular Management: Allows different Intermediate CAs to follow distinct policies while still adhering to the overall trust of the Root CA.
• Revocation Flexibility: Enables individual Intermediate CAs to revoke certificates without affecting the entire PKI.
• Scalability: Facilitates the management of a large number of certificates by distributing responsibilities.
• Compliance: Intermediate CAs can enforce compliance with specific industry or organizational standards.

Considerations for Using Intermediate CAs:

• Security: Protect the private key of the Intermediate CA as it has the power to issue certificates.
• Revocation: Ensure proper procedures for revoking certificates issued by the Intermediate CA.
• Key Management: Properly manage private keys associated with the Intermediate CA.
• Backup and Recovery: Establish backup and recovery mechanisms for Intermediate CA operations and data.
• Monitoring: Regularly monitor the Intermediate CA's operations and certificate status.

An Intermediate Certificate Authority enhances the security and management of a PKI by serving as an intermediary between the Root CA and end-entity CAs, ensuring the secure issuance and management of digital certificates.