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Cybersecurity · head to head

Cosign vs OpenVPN

Cosign logo

Cosign

Cybersecurity

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

From
Free
Rated
-
Full reviewWebsite
OpenVPN logo

OpenVPN

Networking

Open source VPN protocol with a commercial Access Server product priced per simultaneous connection

From
Free
Rated
-
Full reviewWebsite

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.; OpenVPN open source OpenVPN, while free, requires real technical skill to configure, secure and maintain without the Access Server admin layer
  • They diverge on capability: Cosign covers Keyless signing, OpenVPN covers Open source core.
  • Prices and features above were last checked on 1 September 2026.

Where they differ

Only the attributes on which Cosign and OpenVPN actually diverge.

Attributes where Cosign and OpenVPN differ
AttributeCosignOpenVPN
Pricing modelOpen source, no licence feeOpen source core is free; Access Server billed per simultaneous connection
PlatformsmacOS, Linux, Windows, DockerLinux, Windows, macOS, iOS, Android
CategoryCybersecurityNetworking

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 OpenVPN

  • Open source core
  • Access Server admin UI
  • Per-connection licensing
  • Free tier
  • Cross-platform clients

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

OpenVPN

  • A technical team wanting a fully free, self-configured VPN server using the open source protocol without any vendor relationshipnot Cosign
  • A small business wanting a supported, easier-to-administer VPN server, willing to pay per concurrent connection rather than per employeenot Cosign
  • An organisation with more staff than typical concurrent VPN usage, since Access Server bills only active simultaneous connections, not total accountsnot Cosign
  • An IoT or large-scale deployment needing custom Enterprise pricing above 2,000 connectionsnot 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.

OpenVPN

  • Open source OpenVPN, while free, requires real technical skill to configure, secure and maintain without the Access Server admin layer
  • Per-connection billing on Access Server means usage spikes, such as an all-hands remote day, can push simultaneous connections over a licensed limit and block new connections until usage drops or the plan is upgraded
  • OpenVPN's traditional hub-and-spoke architecture routes traffic through a central server, unlike mesh VPN tools like Tailscale or NetBird that establish direct peer-to-peer connections where possible, which can add latency
  • Client configuration and certificate management for the open source version is more manual and error-prone than newer VPN tools with zero-config onboarding
  • Access Server pricing above the Growth tier reverts to custom Enterprise quoting, so very large deployments lose the pricing transparency of the lower tiers
  • The protocol's throughput is generally lower than newer kernel-integrated protocols like WireGuard under equivalent conditions, which matters for high-bandwidth use cases

Pricing, plan by plan

Cosign

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

OpenVPN

Free
  • Access Server FreeFree
    • Up to 2 simultaneous connections
    • All features included
  • Access Server Growth$7/month
    • Per simultaneous connection beyond the free tier
    • Annual billing
  • Access Server Enterprise/IoT$undefined/month
    • Custom pricing for 2,000+ connections

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 OpenVPN if

  • You need open source core.
  • You want to start without paying.
  • You work on Linux, Windows, macOS, iOS, Android.
  • You also want access server admin ui.
OpenVPN review

Questions people ask

Is Cosign or OpenVPN better?
Neither clearly leads. Cosign starts at Free and OpenVPN at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Cosign or OpenVPN?
Cosign starts at Free and OpenVPN at Free.
Does Cosign or OpenVPN run on more platforms?
Cosign runs on macOS, Linux, Windows, Docker. OpenVPN runs on Linux, Windows, macOS, iOS, Android.
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 OpenVPN is typically brought in for.
What can Cosign do that OpenVPN cannot?
Cosign covers Keyless signing, Key and KMS signing, Registry-native storage, In-toto attestations. OpenVPN covers Open source core, Access Server admin UI, Per-connection licensing, Free tier.

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.

OpenVPN: Is OpenVPN free?

The open source protocol and software are free under the GPL; Access Server, the commercial packaged product, charges per simultaneous connection beyond a free 2-connection tier.

Cosign: Is signing alone enough?

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

OpenVPN: What counts as a connection for billing purposes?

A simultaneously active connected device, not a registered user account or total device count; unlimited accounts and devices can be created but only the licensed number can be connected at once.

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.

OpenVPN: How does OpenVPN compare with WireGuard-based tools like Tailscale?

OpenVPN uses a traditional hub-and-spoke VPN architecture rather than the mesh, peer-to-peer approach used by newer tools like Tailscale or NetBird.

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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