Cybersecurity · head to head
Cosign vs Nebula
Cosign
Cybersecurity
Signs and verifies container images and artifacts, with or without managing keys
- From
- Free
- Rated
- -
Nebula
Networking
Certificate based overlay network from Slack, with identity and firewall rules carried in the certificate
- 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.; Nebula the open source project has no user interface, no enrolment workflow and no revocation service, so certificate issuing, distribution and expiry become scripts you write and then have to keep working.
- They diverge on capability: Cosign covers Keyless signing, Nebula covers Certificate carried identity.
- Prices and features above were last checked on 31 August 2026.
Where they differ
Only the attributes on which Cosign and Nebula actually diverge.
Identical on both: starting price (Free), pricing model (Open source, no licence fee), 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 Nebula
- Certificate carried identity
- Group based host firewall
- Lighthouse discovery
- Noise protocol encryption
- Unsafe routes
- Managed option
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 Nebula
- Attaching a signed bill of materials to a release so consumers can verify its provenancenot Nebula
- Meeting a customer or regulatory requirement for signed artifactsnot Nebula
- Verifying third-party images before they enter an internal registrynot Nebula
Nebula
- Flattening a network across several clouds and datacentres without VPC peering or route tablesnot Cosign
- Very large fleets where a central policy service on the connection path is unacceptablenot Cosign
- Environments that already run an internal certificate authority and want the network to use itnot Cosign
- Replacing per host iptables rules with policy written against roles that follow the hostnot 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.
Nebula
- The open source project has no user interface, no enrolment workflow and no revocation service, so certificate issuing, distribution and expiry become scripts you write and then have to keep working.
- Revoking a compromised host means distributing a blocklist entry to every other host and reloading them, which is a fleet wide operation rather than a click, and easy to get wrong under pressure.
- Changing a host group membership means reissuing and redeploying its certificate, so policy changes are a deployment rather than a configuration edit.
- There is no identity provider integration or single sign on in the open source version, so it maps well to servers and badly to a fleet of user laptops.
- NAT traversal is best effort and hosts behind symmetric NAT need a relay configured deliberately, so connectivity failures show up as intermittent rather than immediate and are awkward to diagnose.
Pricing, plan by plan
Cosign
Free- CosignFree
- Apache-2.0
- Public Sigstore infrastructure free to use
- No usage limits published
Nebula
Free- NebulaFree
- Full functionality under the MIT licence
- No host limit
- You operate the certificate authority and lighthouses
- Defined Networking$undefined/month
- Hosted control plane and enrolment
- Managed certificate lifecycle and revocation
- Policy and DNS interface
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 Nebula if
- You need certificate carried identity.
- You want to start without paying.
- You work on Linux, macOS, Windows, iOS, Android, FreeBSD.
- You also want group based host firewall.
Questions people ask
- Is Cosign or Nebula better?
- Neither clearly leads. Cosign starts at Free and Nebula at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
- Which is cheaper, Cosign or Nebula?
- Cosign starts at Free and Nebula at Free.
- Does Cosign or Nebula run on more platforms?
- Cosign runs on macOS, Linux, Windows, Docker. Nebula runs on Linux, macOS, Windows, iOS, Android, FreeBSD.
- 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 Nebula is typically brought in for.
- What can Cosign do that Nebula cannot?
- Cosign covers Keyless signing, Key and KMS signing, Registry-native storage, In-toto attestations. Nebula covers Certificate carried identity, Group based host firewall, Lighthouse discovery, Noise protocol encryption.
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.
Nebula: Does it use WireGuard?
No. Nebula predates the common WireGuard mesh tools and uses the Noise protocol framework with its own certificate format.
Cosign: Is signing alone enough?
No. Verification is a command somebody runs. Without an admission controller enforcing it, an unsigned image still runs.
Nebula: Can I run it without Defined Networking?
Yes, entirely. Defined Networking sells the control plane conveniences, not the network itself.
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.
Nebula: How do I revoke a host?
Add its certificate fingerprint to the blocklist in the configuration of the other hosts and reload them. There is no online revocation check.
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.
Nebula: Is it a good fit for laptops?
Less so than the identity provider based tools. There is no single sign on, so every laptop needs a certificate issued and renewed by whatever process you build.
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.
Related pages
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