Cybersecurity · head to head
Cosign vs SST
Cosign
Cybersecurity
Signs and verifies container images and artifacts, with or without managing keys
- From
- Free
- Rated
- -
The short version
- Each has a real cost: 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.; SST primarily optimized for AWS with Cloudflare support
- They diverge on capability: Cosign covers Keyless signing, SST covers Single config file.
- Prices and features above were last checked on 31 August 2026.
Where they differ
Only the attributes on which Cosign and SST actually diverge.
Identical on both: starting price (Free), free tier (Yes), user rating (Not yet rated).
What each one covers
Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.
Only in Cosign
- Keyless signing
- Key and KMS signing
- Registry-native storage
- In-toto attestations
- Offline verification
- Trusted root and signing config
Only in SST
- Single config file
- Resource linking
- Local development
- Multi-cloud support
- Multiple deployment stages
- VPC tunneling
What people use each for
The jobs each tool is most often brought in to do.
Cosign
- Signing container images in a build pipeline without managing long-lived private keysnot SST
- Attaching a signed bill of materials to a release so consumers can verify its provenancenot SST
- Meeting a customer or regulatory requirement for signed artifactsnot SST
- Verifying third-party images before they enter an internal registrynot SST
SST
- Deploying Next.js frontends with serverless backendsnot Cosign
- Managing databases and storage alongside application codenot Cosign
- Creating staging environments for feature testingnot Cosign
Where each one falls short
Documented limitations, not opinions. Every one is a constraint you would hit in normal use.
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.
SST
- Primarily optimized for AWS with Cloudflare support
- Learning curve for developers unfamiliar with infrastructure concepts
- Limited documentation for some advanced use cases
Pricing, plan by plan
Cosign
Free- CosignFree
- Apache-2.0
- Public Sigstore infrastructure free to use
- No usage limits published
SST
FreeNo published plan breakdown. See the SST review.
Which should you pick?
Choose Cosign if
- You need keyless signing.
- You want to start without paying.
- You work on macOS, Linux, Windows, Docker.
- You also want key and kms signing.
Choose SST if
- You need single config file.
- You want to start without paying.
- You work on AWS, Cloudflare, Node.js.
- You also want resource linking.
Questions people ask
- Is Cosign or SST better?
- Neither clearly leads. Cosign starts at Free and SST at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
- Which is cheaper, Cosign or SST?
- Cosign starts at Free and SST at Free.
- Does Cosign or SST run on more platforms?
- Cosign runs on macOS, Linux, Windows, Docker. SST runs on AWS, Cloudflare, Node.js.
- Can I use Cosign for free?
- Both have a free tier, so you can try either at no cost before committing.
- What is Cosign best used for?
- Cosign is most often used 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. Of those, signing container images in a build pipeline without managing long-lived private keys and attaching a signed bill of materials to a release so consumers can verify its provenance are not what SST is typically brought in for.
- What can Cosign do that SST cannot?
- Cosign covers Keyless signing, Key and KMS signing, Registry-native storage, In-toto attestations. SST covers Single config file, Resource linking, Local development, Multi-cloud support.
Answered from the vendors’ own pages
Cosign: 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.
SST: Is SST free?
Yes, SST is open source and free. You only pay for cloud resources from AWS and other providers.
SourceCosign: Is signing alone enough?
No. Verification is a command somebody runs. Without an admission controller enforcing it, an unsigned image still runs.
SST: What cloud providers does SST support?
SST supports over 150 providers through built-in AWS and Cloudflare components, plus Pulumi and Terraform providers.
SourceCosign: 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.
Cosign: 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.
Cosign: 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.
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