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Design a PKI for internal mTLS and certificates
X.509 Certificates and PKI FundamentalsmTLSHardware Security Modules and Key ManagemeCertificate Revocation MechanismsCA Hierarchy Design
System Design Prompt
Design a Public Key Infrastructure (PKI) for an organization to issue and manage certificates.
Primary Use Cases
- Internal mTLS between services
Optional Extensions
- User/device certificates
- Code signing or document signing
Requirements
- Secure certificate issuance and renewal, with a preference for automation.
- Robust certificate revocation mechanisms for compromised keys or terminated entities.
- Strong key protection, leveraging Hardware Security Modules (HSM) or Key Management Systems (KMS) where appropriate.
- Support for multiple environments (development, staging, production) and potentially multiple geographical regions.
- Auditable operations and a clear incident response plan.
Deliverables
- A proposed CA hierarchy design (e.g., root CA, intermediate CAs).
- Detailed workflows for certificate issuance and renewal.
- An approach to certificate revocation (e.g., CRL, OCSP), including a discussion of their respective trade-offs.
- Strategies for key management, rotation, and disaster recovery for the PKI itself.
- An operational model covering access control and auditing practices.
AI interview prep
Core dilemma
Balancing the absolute security requirements and trustworthiness of a Public Key Infrastructure with the operational complexity, automation needs, and scalability demands of a large, dynamic enterprise.
Mid-level signals3
Senior signals5
Red flags4
3 tradeoffs and 3 stress tests locked
Interview prep
Unlock the interviewer X-Ray rubric, tradeoff matrix, stress tests, clarifying questions, and key concepts.
Design a PKI for internal mTLS and certificates
X.509 Certificates and PKI FundamentalsmTLSHardware Security Modules and Key ManagemeCertificate Revocation MechanismsCA Hierarchy Design
System Design Prompt
Design a Public Key Infrastructure (PKI) for an organization to issue and manage certificates.
Primary Use Cases
- Internal mTLS between services
Optional Extensions
- User/device certificates
- Code signing or document signing
Requirements
- Secure certificate issuance and renewal, with a preference for automation.
- Robust certificate revocation mechanisms for compromised keys or terminated entities.
- Strong key protection, leveraging Hardware Security Modules (HSM) or Key Management Systems (KMS) where appropriate.
- Support for multiple environments (development, staging, production) and potentially multiple geographical regions.
- Auditable operations and a clear incident response plan.
Deliverables
- A proposed CA hierarchy design (e.g., root CA, intermediate CAs).
- Detailed workflows for certificate issuance and renewal.
- An approach to certificate revocation (e.g., CRL, OCSP), including a discussion of their respective trade-offs.
- Strategies for key management, rotation, and disaster recovery for the PKI itself.
- An operational model covering access control and auditing practices.