At Convert Edge, we don't just manage secrets; we engineer the Root of Trust for our clients' entire digital infrastructure. The industry standard for data protection is shifting from simple access control to complex, multi-layered encryption governance. To meet the stringent security and compliance requirements of modern cloud and hybrid architectures, we've developed an advanced, custom Key Management Service (KMS) solution built on HashiCorp Vault.
This initiative moves beyond Vault's standard Transit Secrets Engine to provide clients with a true, fully auditable "Bring Your Own Key" (BYOK) capability and a consistent cryptographic workflow that spans clouds and data centers.
The Technical Imperative: Why Custom KMS?
While cloud-native Key Management Services (AWS KMS, Azure Key Vault, GCP Cloud KMS) offer powerful features, relying solely on them introduces vendor lock-in and creates compliance challenges in multi-cloud and hybrid environments. The core technological uncertainty we addressed was:
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How can we build a unified, identity-based KMS layer using HashiCorp Vault that centralizes policy enforcement and audit trails while maintaining keys within an external, tamper-resistant environment (e.g., a specific cloud KMS or dedicated HSM) to meet strict data sovereignty requirements, without re-engineering every application's encryption logic?
This was not achievable using off-the-shelf Vault configurations, which often delegate key policy and lifecycle management entirely to the external service, creating a fragmented security posture.
Our Custom KMS Development Work
Our experimental development focused on creating a bespoke secrets engine (a Go-based plugin for HashiCorp Vault) that provided the missing orchestration layer for cross-cloud Key Management.
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Phase I: Protocol Interfacing and Proof-of-Concept:
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We began by testing various methods for secure, programmatic key material transfer between Vault's internal generation mechanisms and external KMS providers. Initial attempts to use the existing Managed Key feature for Azure Key Vault failed to provide the necessary granular, fine-grained control over key rotation policy dictated by client requirements, forcing a shift in approach.
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Work Performed: We developed an initial proof-of-concept for a custom Vault secrets engine module designed to interface directly with the KMIP (Key Management Interoperability Protocol) standard, bypassing some of the cloud-specific API limitations we encountered. We conducted unit tests measuring key creation latency, aiming for sub-second key generation throughput.
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Phase II: Custom Key Lifecycle Orchestration:
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The core challenge was ensuring a single, centralized policy dictated by Vault governed the full key lifecycle—generation, rotation, destruction—across heterogeneous backends.
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Work Performed: We engineered a custom key wrapping and unwrapping routine within the Vault plugin. This routine utilized the external KMS as a Hardware Security Module (HSM), where the private key material is generated and stored externally, and only a wrapped Data Encryption Key (DEK) is passed through Vault's policy layer for application consumption. The manipulated variable was the key rotation trigger logic, which we shifted from time-based to usage-count based, governed exclusively by Vault's lease mechanism, achieving automatic, usage-driven key rotation.
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Phase III: Identity-Based Cryptographic Access (BYOK):
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We successfully demonstrated that a client application could authenticate to Convert Edge's custom Vault instance via AppRole, request an encryption key by name, and receive a DEK encrypted by a Master Key residing securely in a separate, non-Vault-managed KMS (e.g., AWS KMS).
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Work Performed: We instrumented the final engine to leverage Vault's identity layer to enforce access control lists (ACLs) for cryptographic operations. We used Prometheus and Grafana for observation, measuring the authorization decision latency. We achieved an authorization overhead of less than 10ms per cryptographic request, validating that our custom KMS could enforce multi-factor, identity-based policies without compromising application performance.
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Technological Advantages Achieved
The work resulted in a custom KMS solution that achieves a level of centralized, cross-platform cryptographic governance previously unavailable to our clients, fundamentally improving their security posture over fragmented commercial solutions.
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Unified, Identity-Based Policy Enforcement: We established a single, consistent mechanism in Vault's policy layer to govern key usage across disparate KMS backends. This eliminated the need to define duplicate, potentially conflicting access policies in each cloud provider's KMS interface, reducing the attack surface.
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Granular BYOK Control: Our system provides the ability to generate and store key material in a specific client-owned, external KMS (meeting regulatory requirements for key origin and custody) while centralizing the audit log and key rotation logic within the vendor-agnostic HashiCorp Vault framework.
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Enhanced Auditability and Compliance: Every key operation, from generation to consumption for decryption, is logged via Vault's secure audit backend, generating a cryptographically verifiable trail that is crucial for meeting compliance standards like PCI DSS and HIPAA. This unified audit log eliminates complex log aggregation from multiple, non-standard cloud KMS logs.