FR-IMG-004 — Image Signing

Go to Crucible Image Management Requirements

Statement

Crucible SHALL associate a digital signature with an identified Image.

Source Statement

Crucible SHALL perform Image Signing by generating a Digital Signature for an identified Image and associating the Digital Signature with that Image.

Source

Crucible System Requirements Specification, Version 1.1 Draft, Functional Requirements, FR-IMG-004.

Assessment

The source statement expresses the approved intent but does not provide a fully testable formulation.

The following Specification, Discipline, and Authoring findings apply:

The system does not use the defined system nameshall does not follow the established uppercase normative conventionSupport is a weak verb that does not identify the required behaviorImage signing does not identify the Image to which the signature appliesThe source statement does not identify the observable result of the signing operationThe source statement does not require verification of the resulting signatureThe source statement does not prescribe a signing algorithm, signature format, key-management system, repository, or implementation technologyThe normalized Statement:

Replaces The system with CrucibleReplaces support with the direct behavior associateIdentifies an Image as the subject of the signing operationIdentifies a digital signature associated with the Image as the required resultRetains one primary required behaviorPreserves implementation independenceThe normalized Statement does not add requirements for signature verification, Image approval, promotion, publication, deployment, or key governance. Separate requirements define those obligations.

Rationale

A digital signature associated with an identified Image allows an actor or process to evaluate whether the signature corresponds to that Image and an applicable signing identity.

Image signing contributes to:

Image authenticity evaluationImage integrity evaluationIdentification of the signing identityControlled Image distributionControlled Image promotionProvenanceAuditabilityTraceabilityThe signing operation may apply to:

A Machine ImageA Container ImageIdentifying Image metadataAn Image content digestA representation containing the Image and associated metadataThe applicable architecture and lower-level requirements determine the exact signed representation and signing mechanism.

Applies To

This requirement applies to:

Image identifiersImage content digestsDigital signaturesSigning identitiesSigning operationsImage repositoriesImage build workflowsImage promotion workflowsCI/CD Pipelines

Verification

Verification SHALL confirm that Crucible performs a signing operation for an identified ImageVerification SHALL confirm that the signing operation associates a digital signature with the identified ImageVerification SHALL confirm that the associated digital signature identifies or references the Image to which it appliesVerification may include:

Machine Image signing testsContainer Image signing testsSignature-record inspectionImage-metadata inspectionImage-digest comparisonSigning-log inspectionAutomated CI/CD Pipeline testingThe verification record SHALL identify:

The signed ImageThe Image identifierThe signed representationThe signing operationThe associated digital signatureThe signing resultThe observed outputThe generated Evidence

Outgoing Traceability

This requirement realizes:

This requirement relates to:

Referenced By

The wiki Backlinks function provides the current list of pages that reference FR-IMG-004.

Incoming Traceability should be derived dynamically from backlinks rather than maintained as a duplicate manual list.

Backlinks identify incoming references but do not define the semantics of each relationship. Referencing pages should identify whether the relationship represents realization, refinement, verification, dependency, or another defined traceability relationship.

ConOps Relationship

The Crucible Concept of Operations describes a Phase 1 workflow that builds controlled Image Artifacts through an automated CI/CD Pipeline.

FR-IMG-004 establishes the required signing behavior for an identified Image produced or processed by that workflow.

Requirements governing Image building, signature verification, promotion, compliance assessment, publication, transfer, and deployment define separate behavior.

Delivery Phase

Phase 1

Implementation Status

Not Assessed

Implementation status requires verification that Crucible associates a digital signature with an identified Image.

Requirement Status

Draft

The source System Requirements Specification identifies Version 1.1 as a draft.

Notes for Editors

This requirement page should retain the stable requirement identifier FR-IMG-004.

Changes to the Statement SHALL preserve the approved intent of the source requirement.

The Source Statement should preserve the original wording from the controlling System Requirements Specification.

The Statement should remain limited to associating a digital signature with an identified Image.

Requirements for signature verification, Image approval, promotion, publication, transfer, and deployment should remain in their applicable requirement pages.

Verification criteria should test only the behavior stated in the normalized Statement and should not introduce additional normative obligations.

Incoming Traceability should use the wiki Backlinks function rather than a manually maintained list.

To reference this requirement Statement from another wiki page, insert:

{{section>dido:02-crusible:99-annexes:annex-c-requirements:03-functional-requirements:03-02-image-management:fr-img-004#Statement&noheader&nofooter&noeditbtn}}

Do not rename this page after an external citation unless a redirect or move plan is in place.

© 2026 Dido Solutions, Inc. and Jackrabbit Consulting, Inc.