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Cybersecurity · head to head

Cosign vs GNAT Pro

Cosign logo

Cosign

Cybersecurity

Signs and verifies container images and artifacts, with or without managing keys

From
Free
Free plan
Yes
Full reviewWebsite
GNAT Pro logo

GNAT Pro

Developer Tools

Software development environments and toolchains for Ada, C/C++ and Rust

From
On request
Free plan
No
Full reviewWebsite

The short version

  • Only Cosign has a free tier, so it costs nothing to try first.
  • 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.; GNAT Pro no pricing published on website; requires contacting AdaCore directly for quotes
  • Prices and features above were last checked on 31 August 2026.

Where they differ

Only the attributes on which Cosign and GNAT Pro actually diverge.

Attributes where Cosign and GNAT Pro differ
AttributeCosignGNAT Pro
Starting priceFreeOn request
Pricing modelOpen source, no licence feequote
Free tierYesNo
PlatformsmacOS, Linux, Windows, DockerWeb
CategoryCybersecurityDeveloper Tools

Identical on both: 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 GNAT Pro

Nothing recorded that Cosign does not also cover.

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 GNAT Pro
  • Attaching a signed bill of materials to a release so consumers can verify its provenancenot GNAT Pro
  • Meeting a customer or regulatory requirement for signed artifactsnot GNAT Pro
  • Verifying third-party images before they enter an internal registrynot GNAT Pro

GNAT Pro

  • Building certified avionics software meeting DO-178B/C standardsnot Cosign
  • Developing automotive embedded systems with ISO-26262 compliancenot Cosign
  • Integrating Ada, C/C++, and Rust components in single codebasenot Cosign
  • Managing software supply chain vulnerabilities and SBOMsnot Cosign
  • Supporting long-lived software systems spanning decadesnot 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.

GNAT Pro

  • No pricing published on website; requires contacting AdaCore directly for quotes
  • Vendor indicates per-user, per-year subscription model but does not disclose specific costs

Pricing, plan by plan

Cosign

Free
  • CosignFree
    • Apache-2.0
    • Public Sigstore infrastructure free to use
    • No usage limits published

GNAT Pro

On request

No published plan breakdown. See the GNAT Pro 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.
Cosign review

Choose GNAT Pro if

Nothing in the data separates GNAT Pro from Cosign on the points above - pick on price and on how each one feels to use.

GNAT Pro review

Questions people ask

Is Cosign or GNAT Pro better?
Neither clearly leads. Cosign starts at Free and GNAT Pro at On request, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Cosign or GNAT Pro?
Cosign has a free tier; the other does not. Paid plans start at Free for Cosign and On request for GNAT Pro.
Does Cosign or GNAT Pro run on more platforms?
Cosign runs on macOS, Linux, Windows, Docker. GNAT Pro runs on Web.
Can I use Cosign for free?
Yes. Cosign has a free tier, so you can try it without paying. GNAT Pro starts at On request.
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 GNAT Pro is typically brought in for.
What can Cosign do that GNAT Pro cannot?
Cosign covers Keyless signing, Key and KMS signing, Registry-native storage, In-toto attestations.

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.

GNAT Pro: How much does GNAT Pro cost?

GNAT Pro pricing is not published on the website. Customers must request a pricing quote by contacting AdaCore directly or speaking with a GNAT Pro expert.

Source
Cosign: Is signing alone enough?

No. Verification is a command somebody runs. Without an admission controller enforcing it, an unsigned image still runs.

GNAT Pro: What is GNAT Pro licensing model?

GNAT Pro is sold on a per-user, per-year basis with no license locks. Customers can request pricing for their specific needs.

Source
Cosign: 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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