Lesson 5.3 · 15 min read

Azure confidential computing, attestation and secure key release

Confidential VM series, application enclaves, Microsoft Azure Attestation, and key release policies.

Azure offerings

Microsoft Azure provides confidential VMs based on AMD SEV-SNP and Intel TDX, Intel SGX-based application enclaves, confidential containers, and confidential GPU VMs. VM series names change as hardware generations roll out, so always check the current list; at the time of writing, Azure's confidential VM documentation includes the AMD-based DCasv5 and ECasv5 families, newer v6 families, and the NCCadsH100v5 series with NVIDIA H100 GPUs.

Microsoft Azure Attestation (MAA)

MAA is a verifier service. It accepts evidence from TEEs (for example SGX quotes, or SEV-SNP and TDX evidence collected by the guest), evaluates it against a configurable policy, and returns a signed JWT attestation token. This is the passport model from Module 3: downstream services check the token rather than raw hardware evidence.

Secure key release (SKR)

Azure Key Vault (Premium) and Managed HSM support keys marked as exportable only under a release policy. The policy states which attestation authority's tokens are accepted and which claims must be present. When a confidential VM presents a valid MAA token that satisfies the policy, the key is released wrapped to a key held by the TEE.

json

{
  "version": "1.0.0",
  "anyOf": [
    {
      "authority": "https://<your-maa-instance>.attest.azure.net",
      "allOf": [
        { "claim": "x-ms-isolation-tee.x-ms-attestation-type", "equals": "sevsnpvm" },
        { "claim": "x-ms-isolation-tee.x-ms-compliance-status", "equals": "azure-compliant-cvm" }
      ]
    }
  ]
}

Release policy shape. Confirm claim names against the Key Vault policy grammar for your TEE type.

Key release across the three major clouds
Cloud	Verifier	Relying party pattern
AWS	KMS appraises Nitro attestation documents directly	Background-check, via key policy conditions
Google Cloud	Google Cloud attestation service issues OIDC tokens	Passport, via workload identity federation
Azure	Microsoft Azure Attestation issues JWTs	Passport, via Key Vault / Managed HSM release policy

Key takeaways

Azure confidential VMs run on AMD SEV-SNP and Intel TDX; confidential GPU VMs use NVIDIA H100.
Microsoft Azure Attestation is a verifier that issues JWTs; secure key release consumes them.
All three clouds implement the same idea: release keys only to an environment whose attestation satisfies a policy you control.

References: Azure confidential VMs, Microsoft Azure Attestation, Secure key release, Key release policy grammar.

End of module 5

Take the module 5 quiz to check your understanding.