Most organizations that know they should sign their images still don’t. Not because they disagree, but because the path to doing it well has been too long. The result is a delivery pipeline built on trust that nobody can verify.The problem spaceUnsigned container images create an open door for attackers at every stage of the delivery pipeline. Malicious images masquerade as legitimate packages, waiting to be pulled by an unsuspecting team. Compromised CI/CD pipelines silently inject tampered artifacts into production builds with no cryptographic evidence of modification. Stolen credentials let a bad actor impersonate a trusted publisher. Even within a single organization, inconsistent practice means some teams sign while others skip the step entirely, leaving gaps in the chain of trust that nobody has mapped. Compounding all of it is base image inheritance. Every container image inherits the security posture of its parent, so one compromised base image can propagate across dozens of downstream services before anyone notices.“Scanning is fundamentally reactive. One tells you what is inside. The other tells you whether you can trust it.”Scanning is fundamentally reactive. It answers, “what vulnerabilities exist in this image?” It cannot answer the question that matters more as artifacts get harder to inspect: “who built this, and has it been modified since it left the build system?” That is the domain of cryptographic signing, which provides proactive provenance. The two are complementary, not interchangeable. One tells you what is inside. The other tells you whether you can trust it. Why the AI era makes this urgentThe workloads have changed faster than the tooling. Model weights, training datasets, inference runtimes, and agent tooling increasingly ship as OCI artifacts. A pickled PyTorch checkpoint itself has no CVE to match against. Safer serialization formats like .safetensors remove the code execution path, but they say nothing about who produced the weights or whether they’re the ones you meant to load. There is no vulnerability database for a set of trained weights, and the CVE and SCA based scanning that registries run has nothing to compare them to. This is not theoretical. In February 2024, JFrog researchers found a malicious PyTorch model on Hugging Face that opened a reverse shell the moment it loaded, abusing pickle’s __reduce__ hook to execute arbitrary code on torch.load(). Their analysis surfaced roughly 100 models on the hub carrying genuinely malicious payloads. No CVE fired, because there was nothing for a CVE to describe. The malice lived in the serialized weights. Model-specific scanning has since appeared to close that gap. Hugging Face runs ClamAV plus a pickle import scan on every file pushed to the Hub, statically disassembling the pickle’s opcode stream to flag dangerous imports. While they help, they are also already being evaded. In February 2025, ReversingLabs described nullifAI, two models that slipped past picklescan by compressing with 7z instead of ZIP and by corrupting the pickle stream immediately after the payload ran, so static analysis errored out on a file whose reverse shell would have already run. Hugging Face removed the models inside 24 hours and patched picklescan. That is the shape of the problem. Pattern matching scanners are a line that keeps moving, and each one answers whether a file resembles something known to be bad. None of them answers where the file came from.“A tampered application image defaces a page. A tampered AI model artifact corrupts predictions at scale.”AI is widening the attack surface in the same motion. Coding assistants suggest dependencies that never pass a human threat model, and that code gets containerized and shipped faster than review can keep up. The blast radius changed too. A tampered application image defaces a page. A tampered AI model artifact corrupts predictions at scale, poisons recommendations served to millions, or in the agentic case takes actions in production: API calls, tool invocations, spend. And when you consume a pre-trained model, you inherit every upstream decision about its training data and its security with zero visibility into any of them. Provenance stopped being a question about your application code. It became a question about the model, the agent, and the tooling that carries them.But signing is not a checkbox. It is a chain. It only works if every link holds.Why registry is the right layerOperating the registry at the scale of Amazon ECR has taught us something that shaped how we think about supply chain security. Most teams don’t verify images. They verify addresses. An admission policy allows images from your registry account, push credentials belong to the pipeline rather than to people, and a scanner blocks critical CVEs. That stops a lot of attacks. What it can’t do is tell a good image from a bad one once it’s inside the boundary, because registry provenance is a claim about location, not origin. Anything that can write to the repository produces an image that looks legitimate: a leaked CI token, a misconfigured cross-account role, a compromised build step. Digest pinning tells you that you got the bytes you asked for, not that those were the right bytes to ask for. Every container image passes through a registry before it runs. It is the last system in the path that sees every artifact, knows who pushed it, and controls who can pull it. It already holds identity context, already enforces access policy, and already stores the metadata that describes what an image contains. The hard part of image signing is doing it consistently across every team and every pipeline without slowing anyone down. The registry is the only layer that can make it invisible.“The hard part of image signing is doing it consistently across every team. The registry is the only layer that can make it invisible.”Signing does not make forgery impossible. An attacker who fully compromises a trusted signing identity, stealing both the credential and the permission to sign, can produce a validly signed malicious image that passes verification. What signing does is shrink the attack surface. Without it, tampering anywhere in the path works, because nothing downstream checks. With signing and enforcement, none of it works unless the attacker compromises one narrowly scoped signer, and that rogue signature is an auditable event tied to an identity instead of an anonymous overwrite. Revoke the identity and the whole fleet stops trusting it in one change. Signing turns an invisible, unbounded problem into a scoped, attributable, revocable one.The operational tax we set out to removeSigning is a three-step process:Sign: Generate a signature at build or push time, binding the image digest to a verifiable identity. The hard question is custody: who holds the private key, and how is it rotated and protected?Verify: At pull time, and critically before the workload is admitted, check the signature against a trust policy which is a declared list of the identities you trust to have signed what you are about to run.Enforce: A Kubernetes admission controller like Kyverno blocks any image not signed by a trusted identity from ever running. Signing without enforcement changes nothing.Enabling signing comes with operational cost. Engineers had to install and configure client-side tooling like Notation CLI or Cosign, then own their signing keys, certificates, rotation schedules, and revocation lists, then build custom automation to wire signing into every pipeline. Across an enterprise with thousands of uniquely configured pipelines, that rollout took weeks to months. What we wanted to know was whether the registry itself could absorb the cost, so that signing could become a property of pushing an image rather than a project each team takes on. The answer to that question became Amazon ECR Managed Signing.The mechanics are deliberately boring, which took some doing. You create a registry level signing configuration with up to ten rules, each pairing a signing profile with repository filters, and every matching push gets signed from then on.Managed Signing answers the custody question by not giving you the keys. You configure a signing profile in AWS Signer, which pins the signing algorithm, a validity period, and the identity that appears in the signature. Signer keeps the certificate and the private key. This means no signing key ever sits in a repo, a runner, or a build log. Validity defaults to 135 months, so signatures won’t expire on you. Revocation is what you’ll actually use when you find out a build was compromised.Then what gets signed, which is narrower than people assume. Signer signs a small Notary payload whose targetArtifact describes the image manifest: media type, digest, size. Not the image bytes directly. Because the signed material is content addressed, verification becomes a statement about exact bytes. The signature itself lands in the same repository as a detached OCI artifact, typed application/vnd.cncf.notary.signature, with a subject descriptor pointing at the image manifest digest. One image can carry signatures from several profiles as your trust requirements change. Signing happens asynchronously, which keeps Signer off the push path. A synchronous call would turn an availability dip or a throttle into a failed docker push for a developer, and it would put signing latency in front of every pipeline. The push commits first, and ECR calls SignPayload after. Verification and enforcement happen downstream, and the trust policy is where the whole design becomes legible. Your cluster operator writes it and imports it with notation policy import. It’s a short reviewable file:{"version": "1.0","trustPolicies": [ { "name": "aws-signer-tp", "registryScopes": ["*"], "signatureVerification": { "level": "strict" }, "trustStores": ["signingAuthority:aws-signer-ts"], "trustedIdentities": [ "arn:aws:signer:us-east-1:111122223333:/signing-profiles/platform_images" ] } ]}That policy says a workload runs only if it carries a signature chaining to the AWS Signer root and produced by that specific profile. Admission does the work in order: resolve the reference to a digest, fetch the signature via OCI Referrers API, validate the envelope against its embedded certificate chain, walk that chain to the root in the trust store, check the signing identity against trustedIdentities, and check revocation. Revoking a profile makes verification fail wherever that profile is trusted. New admissions stop immediately and running pods pick it up when they’re next rescheduled. On EKS you get there with Gatekeeper and Ratify, or with Kyverno. Both paths use the AWS Signer plugin. Every link is checkable by the cluster itself, from the artifact plus a root certificate without asking the verifier to trust the registry it pulled from, or the pipeline that pushed.ConclusionVulnerability scanning answers a question that mattered in the application era: what is broken inside this image? The AI era asks a harder one that scanning was never built to answer. Can you prove where this came from, and that no one touched it?The cryptography was never the hard part. Making it the path of least resistance was. Sign, verify, and enforce, and let the registry carry the tax so your teams don’t have to.To explore what’s referenced here, see Amazon ECR managed signing and signature verification on Amazon EKS.The post Your container images are unsigned. In the AI era, that’s a ticking time bomb. appeared first on The New Stack.