Design a Secrets Management & KMS Service

Question

Design a system for storing secrets and managing encryption keys with rotation, auditing, and fine-grained access control.

Accepted Answer

Designing a secure system for secrets and encryption keys requires a layered approach focusing on a robust root of trust, secure storage, and comprehensive key lifecycle management, incorporating auditing and granular access controls. Establish a Hardware Security Module (HSM)-backed root of trust for generating and protecting the primary encryption keys. All subsequent encryption keys will be derived from or wrapped by these master keys (envelope encryption), ensuring that sensitive operations occur within a tamper-resistant environment. Implement a dedicated secrets storage solution that leverages Access Control Lists (ACLs) for fine-grained permissions on individual secrets. Utilize leasing and dynamic credentials for secrets like database passwords or API keys, so they are short-lived and automatically rotated or revoked upon expiry or change. Design a key management service (KMS) capable of generating cryptographic keys, managing their versions, performing automated rotations based on policy (e.g., time-based or event-driven), and supporting efficient key revocation mechanisms. Employ an envelope encryption strategy where application secrets are encrypted with data encryption keys (DEKs), and these DEKs are then encrypted with key encryption keys (KEKs) managed by the KMS. This isolates the DEKs and simplifies secret management. Implement comprehensive auditing for all operations within the secrets and key management system. This includes tracking who accessed which secret, when keys were generated, rotated, or revoked, and any failed access attempts, providing a clear trail for compliance and incident response. Integrate the system with existing identity and access management (IAM) solutions to enforce the principle of least privilege. Access to secrets and key management operations should be tied to user roles and responsibilities, further strengthening security and adherence to compliance frameworks. Continuous monitoring of audit logs is crucial for detecting anomalies and potential breaches. Proactive measures such as regular security assessments and vulnerability scanning of the system will ensure its ongoing integrity and resilience against evolving threats.

Design a Secrets Management & KMS Service

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