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Cybersecurity · head to head

Cosign vs Proofpoint

Cosign logo

Cosign

Cybersecurity

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

From
Free
Rated
-
Full reviewWebsite
Proofpoint logo

Proofpoint

Cybersecurity

Email security and data protection suite from a private company owned by Thoma Bravo, licensed per user with modules sold separately.

From
$6/month
Rated
-
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.; Proofpoint licensing is per user per year with each capability as a separate stock item, so the platform shown in a proof of concept is normally several products, and adding awareness training, data loss prevention or insider threat monitoring later is a fresh negotiation rather than enabling a feature.
  • They diverge on capability: Cosign covers Keyless signing, Proofpoint covers Inline secure email gateway.
  • Prices and features above were last checked on 31 August 2026.

Where they differ

Only the attributes on which Cosign and Proofpoint actually diverge.

Attributes where Cosign and Proofpoint differ
AttributeCosignProofpoint
Starting priceFree$6/month
Pricing modelOpen source, no licence feesubscription
Free tierYesNo
PlatformsmacOS, Linux, Windows, DockerEmail, Cloud, Web
FoundedUnknown2002

Identical on both: user rating (Not yet rated), category (Cybersecurity).

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 Proofpoint

  • Inline secure email gateway
  • Attachment sandboxing
  • URL rewriting and click-time analysis
  • Threat Response Auto-Pull
  • Email Fraud Defense
  • Security awareness training
  • Insider Threat Management
  • Enterprise DLP

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

Proofpoint

  • A regulated organisation that needs a filtering layer, DMARC enforcement and archiving with an auditable trail across all threenot Cosign
  • An organisation that suffered a business email compromise and must show its board a control that stops delivery rather than remediating afterwardsnot Cosign
  • Concentrating stronger controls and training on the specific individuals who actually receive targeted attacks rather than applying uniform policynot Cosign
  • Retracting a phishing message from thousands of mailboxes after the verdict changes, including copies that were forwarded internallynot 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.

Proofpoint

  • Licensing is per user per year with each capability as a separate stock item, so the platform shown in a proof of concept is normally several products, and adding awareness training, data loss prevention or insider threat monitoring later is a fresh negotiation rather than enabling a feature.
  • It sits inline with MX records pointed at it, so any service degradation is a mail outage for the entire organisation, and both migrating on and migrating off are cutovers with queueing, rollback planning and a real risk of message loss.
  • Most customers on Microsoft 365 E5 or Google Workspace Enterprise are already paying for native filtering, so Proofpoint is a second licence layered over a capability the organisation owns, and that comparison is raised by finance at every single renewal.
  • The administration console carries a decade of acquisitions: the classic gateway policy routes and filters do not share a model with the newer module interfaces, rule evaluation is order-sensitive in ways that surprise untrained administrators, and mistakes there silently change what is delivered.
  • Quarantine management is a standing helpdesk workload because legitimate bulk mail, invoices and supplier notifications are held, and unless end-user digests are configured and users are taught to use them, the security team becomes the mail release desk.

Pricing, plan by plan

Cosign

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

Proofpoint

$6/month
  • Email Protection$6/month
    • Per user
    • Advanced threat detection
    • Data loss prevention
  • Compliance$8/month
    • All Email Protection
    • Archive & search
    • eDiscovery
  • Advanced Threat$10/month
    • All Compliance features
    • Targeted attack detection
    • Behavior analytics

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 Proofpoint if

  • You need inline secure email gateway.
  • You work on Email, Cloud, Web.
  • You also want attachment sandboxing.
Proofpoint review

Questions people ask

Is Cosign or Proofpoint better?
Neither clearly leads. Cosign starts at Free and Proofpoint at $6/month, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Cosign or Proofpoint?
Cosign has a free tier; the other does not. Paid plans start at Free for Cosign and $6/month for Proofpoint.
Does Cosign or Proofpoint run on more platforms?
Cosign runs on macOS, Linux, Windows, Docker. Proofpoint runs on Email, Cloud, Web.
Can I use Cosign for free?
Yes. Cosign has a free tier, so you can try it without paying. Proofpoint starts at $6/month.
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 Proofpoint is typically brought in for.
What can Cosign do that Proofpoint cannot?
Cosign covers Keyless signing, Key and KMS signing, Registry-native storage, In-toto attestations. Proofpoint covers Inline secure email gateway, Attachment sandboxing, URL rewriting and click-time analysis, Threat Response Auto-Pull.

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.

Proofpoint: Does it replace Microsoft Defender for Office 365?

Functionally it overlaps heavily, and running both means paying twice for filtering. Most Proofpoint customers on Microsoft 365 keep Defender licensed because it is bundled in E5 and use Proofpoint as the inline gateway. Expect to justify that duplication annually.

Cosign: Is signing alone enough?

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

Proofpoint: Who owns Proofpoint?

Thoma Bravo, a private equity firm, which took the company private in 2021. It has continued to acquire since, including Tessian, Normalyze and Hornetsecurity, which is why the portfolio spans so many adjacent categories.

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.

Proofpoint: Do I have to change my MX records?

For the gateway, yes. That is what makes it inline and able to block before delivery. Some newer capabilities integrate through the mailbox API instead, but the core protection model is MX-level.

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.

Proofpoint: Is security awareness training included?

No, it is a separate subscription. It integrates well with the threat data, so training can target the users actually being attacked, but it is a distinct line item on the quote.

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.

Proofpoint: What does Threat Response Auto-Pull actually do?

It removes messages from mailboxes after delivery when the verdict changes, including copies that users forwarded internally. It is the answer to the case where a link was clean at delivery and weaponised an hour later.

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