Supply Chain Attestation
also called SLSA, Provenance Attestation
A signed statement about how an artifact was produced — from which source, by which builder, with which inputs — verified before deployment.
Signing an artifact proves it has not been altered since signing. It says nothing about whether what was signed is what you intended, and the significant supply-chain compromises of recent years exploited exactly that gap: the malicious artifact was legitimately signed, because the attacker compromised the build.
Attestation raises the claim. The build system produces a signed statement recording the source repository and commit, the build definition, the inputs consumed, and the identity of the builder. Admission then verifies not just the signature but the content of the claim: this image must come from this repository, built on this pipeline, from a protected branch.
The framework that structures this is SLSA, and its levels are a useful maturity ladder rather than a certification: from a build that produces provenance, to a build that runs on a hosted service which generates provenance the build itself cannot forge, to hardened builds with two-party review.
The step most estates skip is the last and most important one: verification at deployment. Generating attestations that nothing checks is a cryptographic paper trail with no control attached, and it is common, because generating them is a pipeline change while verifying them means being willing to block a deployment.