Container image signing provides a cryptographic guarantee about the origin and state of an image. The process involves a trusted entity (a developer or an automated build system) signing an image digest with a private key. Verification, typically performed by an admission controller in a Kubernetes cluster before deployment, uses the corresponding public key to confirm two critical security properties:

1. Authenticity: The signature is valid and was created by the holder of the private key, verifying the image's source.

2. Integrity: The image's current digest matches the digest that was originally signed, ensuring the image has not been altered or tampered with since it was created.

B. The primary purpose is establishing trust through authenticity and integrity, not defining legal or organizational ownership, which is a misinterpretation of the concept.

C. Image signing is a security best practice, not a universal mandate. Cloud providers and Kubernetes do not deny unsigned images by default; this enforcement requires explicit configuration.

D. The signature metadata adds a negligible amount to the registry storage, not the image layers, and verification occurs at deployment time, having no impact on the application's runtime performance.

1. Red Hat OpenShift Documentation: In the section on "Signing container images for trusted software supply chains

" it states

"You can use image signatures to resist tampering and to ensure that you are using a trusted image... When you verify the signature before you use the image

you can be sure that the image has not been tampered with and that it is from a trusted source." (Source: Red Hat OpenShift Container Platform 4.14 Documentation

Chapter 3. Signing container images for trusted software supply chains).

2. Google Cloud Documentation (Binary Authorization): "Binary Authorization is a deploy-time security control that ensures only trusted container images are deployed... By checking for verifiable attestations

Binary Authorization enforces that images have successfully passed required processes... before they are deployed." This directly links verification to ensuring integrity and authenticity in a cloud environment. (Source: Google Cloud

Binary Authorization documentation

"Overview").

3. The Linux Foundation (Sigstore/Cosign Project): The official documentation for Cosign

a project for signing container images

states its goal is to make signatures "invisible infrastructure" to "verify the authenticity and integrity of the artifacts." (Source: Sigstore Documentation

"Cosign" section).

4. Kubernetes Documentation: The mechanism for enforcing signature verification is the admission controller. The documentation on "Dynamic Admission Control" explains how webhooks can be used to "validate... requests

" which is the technical foundation for implementing policies that check image signatures before allowing a pod to run. (Source: Kubernetes Documentation

Reference > API Access Control > Dynamic Admission Control).