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Developer Tools · head to head

GNAT Pro vs Sigstore

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
Sigstore logo

Sigstore

Cybersecurity

Free public signing and transparency infrastructure for open source artifacts

From
Free
Free plan
Yes
Full reviewWebsite

The short version

  • Only Sigstore has a free tier, so it costs nothing to try first.
  • Each has a real cost: GNAT Pro no pricing published on website; requires contacting AdaCore directly for quotes; Sigstore the security model depends on somebody watching the log. The documentation states that compromise of an identity provider or of Fulcio itself is detectable only if third parties monitor the transparency log, the monitoring tool is a community-tier rather than core project, and almost no consumer runs one.
  • Prices and features above were last checked on 31 August 2026.

Where they differ

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

Attributes where GNAT Pro and Sigstore differ
AttributeGNAT ProSigstore
Starting priceOn requestFree
Pricing modelquoteOpen source, public instance free to use
Free tierNoYes
PlatformsWebWeb, Linux, macOS, Windows, Self-hosted
CategoryDeveloper ToolsCybersecurity

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 GNAT Pro

Nothing recorded that Sigstore does not also cover.

Only in Sigstore

  • Fulcio
  • Rekor
  • Keyless signing
  • Multi-language clients
  • Timestamp authority
  • Neutral governance

What people use each for

The jobs each tool is most often brought in to do.

GNAT Pro

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

Sigstore

  • Open source projects signing releases without running a certificate authoritynot GNAT Pro
  • Organisations meeting a signed-artifact requirement without buying a signing productnot GNAT Pro
  • Publishing provenance that a consumer can verify independently of younot GNAT Pro
  • Self-hosting the same components where a public log is unacceptablenot GNAT Pro

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

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

Sigstore

  • The security model depends on somebody watching the log. The documentation states that compromise of an identity provider or of Fulcio itself is detectable only if third parties monitor the transparency log, the monitoring tool is a community-tier rather than core project, and almost no consumer runs one.
  • It is a 99.5 percent objective with no service level agreement, which permits several hours of downtime a month and offers no remedy. A pipeline that signs on every build has taken a hard dependency on a free service with no contract behind it.
  • Log scale is a live engineering problem rather than a theoretical one. The active shard holds billions of entries, the log has already been sharded twice, and sharding version 1 requires stopping traffic, which is why a replacement was built.
  • Ten-minute certificates make trust depend on log availability. Verifying an older signature relies on the log entry proving it was made inside that window, so a lost or unreachable entry can render a valid artifact unverifiable.
  • Migration debt is substantial and ongoing. Version 2 of the log is generally available but not the public default, the signing client has an announced breaking release ahead, some official clients lag the new log format, and a post-quantum migration is named as the next break after that.

Pricing, plan by plan

GNAT Pro

On request

No published plan breakdown. See the GNAT Pro review.

Sigstore

Free
  • Public good instanceFree
    • Free to everyone with no contract
    • 99.5 percent availability objective, not an agreement
    • 100KB cap per attestation upload
  • Self-hostedFree
    • Apache-2.0
    • Run your own Fulcio and Rekor
    • Rekor v2 available for self-hosters

Which should you pick?

Choose GNAT Pro if

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

GNAT Pro review

Choose Sigstore if

  • You need fulcio.
  • You want to start without paying.
  • You work on Web, Linux, macOS, Windows, Self-hosted.
  • You also want rekor.
Sigstore review

Questions people ask

Is GNAT Pro or Sigstore better?
Neither clearly leads. GNAT Pro starts at On request and Sigstore at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, GNAT Pro or Sigstore?
Sigstore has a free tier; the other does not. Paid plans start at On request for GNAT Pro and Free for Sigstore.
Does GNAT Pro or Sigstore run on more platforms?
GNAT Pro runs on Web. Sigstore runs on Web, Linux, macOS, Windows, Self-hosted.
Can I use Sigstore for free?
Yes. Sigstore has a free tier, so you can try it without paying. GNAT Pro starts at On request.
What is GNAT Pro best used for?
GNAT Pro is most often used for building certified avionics software meeting do-178b/c standards, developing automotive embedded systems with iso-26262 compliance, integrating ada, c/c++, and rust components in single codebase, managing software supply chain vulnerabilities and sboms. Of those, building certified avionics software meeting do-178b/c standards and developing automotive embedded systems with iso-26262 compliance are not what Sigstore is typically brought in for.
What can GNAT Pro do that Sigstore cannot?
Sigstore covers Fulcio, Rekor, Keyless signing, Multi-language clients.

Answered from the vendors’ own pages

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
Sigstore: Is the public instance really free?

Yes, with no contract and no paid tier. That is also the weakness: a 99.5 percent objective with no agreement, no remedy and support through Slack.

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
Sigstore: Has the public log moved to Rekor v2?

No. Version 2 reached general availability in October 2025 and self-hosters can use it, but the public instance still defaults to version 1 and the project has said it will for the foreseeable future.

Sigstore: Does Sigstore make my dependencies safe?

No, and this is a category error worth avoiding. It tells you who published something. It has no knowledge of what the artifact contains or whether it is vulnerable.

Sigstore: What are the rate limits?

Not published. Only the 100KB cap per attestation upload is documented, so do not design a high-volume pipeline around assumed throughput.

Sigstore: Should we self-host it?

If a public record of every signature is unacceptable, or if a free service with no agreement cannot sit in your build path, then yes. Otherwise the public instance is what most projects use.

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