Cosignvs
Sigstore
Sigstore: The wider project, if the question is the infrastructure rather than the client
Cosign
Signs and verifies container images and artifacts, with or without managing keys
As of 31 August 2026, Cosign is free to use. The Sigstore signing client. Softwr lists it under Cybersecurity. Cosign is made by Sigstore, under the Open Source Security Foundation, available on macOS, Linux, Windows, Docker.
Overview
What Cosign does
Cosign signs container images, blobs and arbitrary artifacts, storing signatures in the OCI registry beside the thing they sign. It supports keyless signing through Sigstore, where a short-lived certificate is issued against an OIDC identity and recorded in a public transparency log, as well as self-managed keys, cloud key management services and hardware tokens. It can attach in-toto attestations, including a bill of materials produced elsewhere. The boundary is worth stating plainly because the marketing around supply chain security blurs it. Cosign attests authorship and integrity. It has no vulnerability knowledge at all: it does not enumerate CVEs, it does not analyse reachability, and while it can carry an SBOM as a signed attestation it never reads what that attestation says. A signature proves an identity signed this artifact. It does not prove the artifact is safe, and it does not prove that identity was entitled to sign it. It also enforces nothing by itself. Verification is a command somebody runs. Turning that into a control that stops an unsigned image from running requires a separate admission controller, and a bare verify command without a pinned certificate identity and issuer accepts a signature from anyone at all, which is close to worthless.
What people use it for
- Signing container images in a build pipeline without managing long-lived private keys
- Attaching a signed bill of materials to a release so consumers can verify its provenance
- Meeting a customer or regulatory requirement for signed artifacts
- Verifying third-party images before they enter an internal registry
Related searches
The honest half
Where it falls short
Concrete and checkable, so you can decide whether any of them matter to you. This is the half of a review a vendor will not write about Cosign.
- Keyless signing inherits every weakness of the identity provider behind it. Sigstore’s own threat model states that if an identity provider is compromised, Sigstore will issue certificates to those identities, so a compromised account produces perfectly valid signatures.
- A signature proves who signed, never whether they should have. The documentation is explicit that Sigstore cannot determine authorisation, so every consumer must write and maintain their own identity and issuer policy or verification means nothing.
- Nothing is enforced without an admission controller. Signing changes what you can prove, not what runs, and the official policy controller has a small maintainer base for a component sitting in a cluster admission path.
- Upgrades break pipelines. Version 3 changed defaults, version 4 is announced as removing legacy functionality and roughly half the command line flags, and two official client libraries still lacked support for the new log format as of mid 2026.
- Signatures do not expire. An artifact signed before a maintainer account was compromised and one signed after are indistinguishable unless somebody is actively monitoring the transparency log, and almost nobody is.
Cross-shopped
What people choose instead of Cosign
Each pairing was judged by two reviewers asking whether a buyer would genuinely weigh the two against each other. The ones that failed were deleted rather than published.
- CosignvsSyft
Syft: A different job entirely: what is inside the artifact rather than who signed it
Pricing
What Cosign costs
Taken from the vendor's own pricing page. Prices move, so check before you buy.
Cosign
Free
- Apache-2.0
- Public Sigstore infrastructure free to use
- No usage limits published
- Community support only
Capabilities
Features
Keyless signing
Short-lived certificates issued against an OIDC identity, with no key material to store
Key and KMS signing
Self-managed keys, AWS, Google, Azure and Vault key management, and PKCS#11 hardware tokens
Registry-native storage
Signatures live in the OCI registry alongside the artifact
In-toto attestations
Attaches signed provenance and bill of materials documents
Offline verification
Verification without contacting the transparency log, added in version 3
Trusted root and signing config
Key and log rotation without requiring every client to upgrade
Answered, with sources
Questions people ask
Each answer names the page it came from, so you can check it rather than take our word for it.
Does Cosign tell me if an image is vulnerable?
No. It has no vulnerability knowledge whatsoever. It can carry an SBOM as a signed attestation but never reads it. Pair it with a scanner.
Is signing alone enough?
No. Verification is a command somebody runs. Without an admission controller enforcing it, an unsigned image still runs.
What does a bare cosign verify actually prove?
Very little. Without a pinned certificate identity and OIDC issuer, it accepts a valid signature from any identity at all.
What is the risk of keyless signing?
Your OIDC provider becomes the root of trust. Compromise of that account yields genuine, verifiable signatures, so account security is the control that matters.
Should we expect breaking changes?
Yes. Version 4 is announced to remove roughly half the flags, and a post-quantum migration is named as a further breaking change after that.
Keep looking
Where to go from Cosign
- Cosign alternativesEvery product people weigh against it
- Cosign pricingPlans, floors and what the tiers exclude
- Cosign badgesWhich rules it meets, and the figure behind each
- All Cybersecurity softwareThe full category
- Best Cybersecurity softwareThe shortlist, and how it was cut
Best Cybersecurity software for
Compare Cosign with
- Sigstore
- Syft
- Chainguard
- HashiCorp Vault
- Infisical
- OWASP ZAP
- Wireshark
- Bitwarden
- Semgrep
- Trivy
- authentik
- Microsoft Intune
- Netwrix
- NordVPN
- Omada Identity
- Ory
- ProtonVPN
- Grype
Other Cybersecurity software
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From $8/mo9 researched notesData access governance and change auditing across Active Directory, file shares and Microsoft 365
Pricing on request11 researched notesConsumer and business VPN from Nord Security, registered in Panama, with repeated third-party no-logs audits.
From $3.99/mo14 researched notesIdentity governance and administration focused on access certification and compliance evidence
Pricing on request11 researched notesOpen-source identity, authentication, and permissions infrastructure
Free, then $64/mo8 researched notes
Softwr does not host reviews and shows no star rating for Cosign, because a rating we did not collect is not ours to publish. What is here is the pricing and platform detail from the vendor’s own pages, limitations we could state concretely, and alternatives a reviewer confirmed people weigh against it. Tell us if any of it is wrong.
More on Cosign
Cosign alternatives
What people switch to, and what they give up
Cosign pricing
Every tier, and where the cost actually lands
Compare Cosign
Put it head to head with anything we hold
Cosign badge
Its rating, and an embed for your own site
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