Production Managed-Key Integration Guide

Issue: #512.

This guide documents the production runtime signing path for AsiBackbone governance residue when a host wants managed-key signing without making AsiBackbone responsible for key custody or cloud/provider-specific key-management behavior.

In this software project, ASI means Accountable Systems Infrastructure. AsiBackbone is a governance spine for accountable decision flow. It is not a key-management platform, HSM appliance, cloud KMS wrapper, compliance certification service, immutable ledger, or legal non-repudiation product by itself.

Important

Production runtime signing remains provider-neutral. AsiBackbone documents how a host can connect Azure Key Vault, AWS KMS, GCP Cloud KMS, HSM, or enterprise key-management clients behind the existing managed-key boundary. AsiBackbone does not ship or maintain first-party production signing providers, production-style signing sample hosts, credentials, key storage, key rotation, legal non-repudiation guarantees, or provider-specific security guarantees.

Decision

The approved production signing-provider story is Option 1: provider-neutral only.

AsiBackbone provides signing and verification abstractions, canonical hashing/signing seams, safe metadata conventions, the AsiBackbone.Signing.ManagedKey adapter boundary, and documentation for host responsibilities.

AsiBackbone does not provide first-party production provider packages for Azure Key Vault, AWS KMS, GCP Cloud KMS, HSM appliances, certificate stores, or enterprise key-management systems. It also does not ship a production-style sample host that could be mistaken for a supported provider implementation.

This keeps the package family focused on governance flow and avoids expanding the project into consumer key-management maintenance.

Three different signing/provenance concerns

Do not collapse these concerns into one claim:

Concern	What it means	AsiBackbone posture
NuGet package signing	Whether published `.nupkg` files are signed release artifacts.	Deferred unless a reviewed package-signing process is adopted. See the consumer verification guide.
GitHub provenance and SBOM	Source Link, repository metadata, package SBOMs, and workflow provenance where available.	Useful supply-chain evidence, but not package signing and not runtime audit signing.
Runtime governance-residue signing	A host signs audit residue, outbox records, or decision receipts through configured signing infrastructure.	Supported through provider-neutral abstractions and the managed-key adapter boundary; production key custody remains host-owned.

A package can have Source Link and SBOM provenance without being maintainer-signed. A governance record can be signed at runtime without proving legal non-repudiation. A signed governance record still requires verification, durable storage controls, key-retention policy, monitoring, and incident response before a host should make stronger integrity claims.

Runtime boundary

The runtime dependency direction stays narrow:

AsiBackbone.Core
        ^
        |
AsiBackbone.Signing.ManagedKey
        ^
        |
Host-owned managed-key client
        ^
        |
Azure Key Vault, AWS KMS, GCP Cloud KMS, HSM, or enterprise KMS

AsiBackbone.Signing.ManagedKey owns the adapter service, provider-neutral options, DI registration helpers, safe metadata handling, retry diagnostics, and fail-closed defaults.

The consuming host owns the concrete client and operating environment.

What AsiBackbone provides

AsiBackbone provides:

IAsiBackboneSigningService and IAsiBackboneSignatureVerificationService abstractions in Core;
canonical payload/hash contracts and signing-ready metadata fields;
IManagedKeySigningClient as the host-owned client boundary;
ManagedKeySigningOptions for provider descriptor, key ID, key version, hash/signature algorithm descriptors, retry settings, and failure behavior;
fail-closed production-oriented registration through AddAsiBackboneManagedKeySigning(...);
local-validation registration for tests, samples, diagnostics, and intentionally unsigned failure metadata;
safe metadata filtering so provider metadata cannot return secrets or overwrite service-owned diagnostic keys.

What the host provides

The consuming host provides:

the Azure Key Vault, AWS KMS, GCP Cloud KMS, HSM, certificate-store, or enterprise key-management client;
authentication and authorization configuration, such as managed identity, workload identity, service account, certificate, or enterprise credential flow;
key custody, key creation, key protection level, key version selection, and key rotation policy;
provider-specific algorithm mapping;
timeout, retry, circuit-breaker, and failover policy;
monitoring and alerting for signing failures, latency, disabled keys, revoked keys, provider outages, and verification failures;
a verification service or verification process when signed records must be trusted later;
durable audit/outbox storage, retention, backup, immutability/append-only controls, and anchoring strategy when required;
legal, compliance, and evidentiary interpretation for the deployed environment.

Minimal host-owned adapter shape

A production host implements IManagedKeySigningClient around its selected provider. The client signs the precomputed AsiBackbone signing hash and returns provider-neutral metadata. It must not return private key material, tokens, secrets, or raw credential material.

services.AddSingleton<IManagedKeySigningClient, HostOwnedManagedKeySigningClient>();

services.AddAsiBackboneManagedKeySigning(options =>
{
    options.ProviderName = "host-managed-key";
    options.KeyId = "provider-specific-key-reference";
    options.KeyVersion = "provider-specific-key-version";
    options.HashAlgorithm = "SHA-256";
    options.SignatureAlgorithm = "RSASSA-PSS-SHA256-MANAGED-KEY";
    options.RequireKeyVersion = true;
    options.ReturnUnsignedOnFailure = false;
    options.MaxRetryAttempts = 2;
});

The concrete HostOwnedManagedKeySigningClient might call Azure Key Vault, AWS KMS, GCP Cloud KMS, an HSM appliance, or an organization-owned signing service. That implementation is intentionally outside the AsiBackbone package boundary.

Provider-specific checklist

Before connecting a concrete provider, document these host-owned choices:

Which provider signs the artifact hash?
Which key ID and key version are active?
Which algorithm descriptor does AsiBackbone record, and which concrete provider algorithm does it map to?
Does the provider sign a digest or require a raw payload?
Which identity can sign?
Which identity can verify or read the public key?
How are signing and verification permissions separated?
How are disabled, retired, missing, or revoked key versions detected?
What happens when the provider times out or is unavailable?
Are signing failures denied, deferred, escalated, dead-lettered, or allowed to continue unsigned under an explicit host policy?
How are provider operation IDs recorded without leaking secrets?
How are records verified after key rotation?
Which dashboards or alerts indicate signing failure rates, latency, and verification failure rates?

Failure posture

Production-oriented managed-key registration fails closed by default because ReturnUnsignedOnFailure defaults to false.

When signing is required for a governed operation, a host should usually treat provider unavailability, unsupported algorithms, key mismatch, missing required key version, or verification failure as a denial, deferral, escalation, or dead-letter condition according to host policy.

Unsigned failure metadata is useful for local validation, diagnostics, and explicitly policy-routed fallback. It is not a successful signature and must not be described as signed governance residue.

Verification path

Signing and verification are separate responsibilities.

A signed record should preserve:

signing hash;
hash algorithm;
signature value or signature reference;
signature algorithm descriptor;
key ID;
key version;
provider descriptor;
signed UTC timestamp;
safe provider operation ID when available.

A host that needs to trust records later must provide a verification path that can resolve the recorded key reference, use the recorded algorithm family, account for retired-key verification, and distinguish invalid signatures from provider unavailability.

Safe wording

Safe wording:

"The governance artifact hash was signed through the host-configured managed-key client."
"AsiBackbone preserved provider-neutral signature metadata returned by the host-owned signing boundary."
"Private key material remains outside AsiBackbone."
"Production signing infrastructure, key custody, rotation, monitoring, verification, and legal interpretation are host-owned."
"The managed-key package is an adapter boundary, not a cloud KMS or HSM provider package."

Avoid wording such as:

"AsiBackbone supports Azure Key Vault/AWS KMS/GCP Cloud KMS/HSM out of the box."
"AsiBackbone provides production key management."
"The managed-key adapter proves legal non-repudiation."
"Signing alone makes records tamper-evident."
"Unsigned failure metadata means the artifact was signed."
"A sample host is a production signing provider."

Non-goals

AsiBackbone does not provide:

production key custody;
cloud KMS SDK wrappers;
first-party Azure Key Vault, AWS KMS, GCP Cloud KMS, HSM, certificate-store, or enterprise KMS signing providers;
production-style signing sample hosts;
credential management;
automatic key creation or rotation;
legal non-repudiation guarantees;
provider-specific compliance guarantees;
immutable storage, blockchain anchoring, or append-only database behavior by default;
tamper-evident records by default;
incident response for a host's key-management environment.

Table of Contents