Does npm (Node.js package manager) provide cryptographic authentication and integrity validation?

npm supports (but doesn't enforce) integrity verification on two levels.

First, registries can sign the packages they provide. The ECDSA signatures are included in a signatures array in the dist object, and the signing keys are published at registry-host.tld/-/npm/v1/keys. Clients can then check the signatures with npm audit signatures.

Additionally, npm allows provenance statements. If the package developer chooses to build and publish their package through a supported CI/CD platform (currently GitHub actions or GitLab CI/CD), then the CI/CD provider can automatically produce a signature over the build information (build environment, commit, build file etc.). The registry additionally signs a publish attestation to confirm that the package was published by an authorized user.

Note, however, that none of this is classical code signing where the developer holds the signing keys. If a registry or the publication process is compromised, then an attacker can still be able to inject malicious packages. And neither package signatures nor provenance statements are mandatory, so it depends on the individual registry and package whether you benefit from the integrity features.

Yes, npm does perform integrity checks, but there are important nuances.

Integrity Verification (SHA-512): Starting from npm v5 (2017), every package published to the npm registry includes a SHA-512 integrity hash in its metadata. When you install a package, npm compares the downloaded tarball against this hash to ensure it hasn’t been modified. This provides tamper-detection beyond simple HTTPS transport.

Authentication of Publishers: npm does not, by default, cryptographically verify the identity of the package author in the way that OS package managers often do. Instead, it relies on the npm registry’s authentication system. Package maintainers authenticate when publishing, and npm attaches the integrity hash. However, the trust model is weaker compared to Debian’s GPG signatures.

Additional Security Features:

npm audit checks for known vulnerabilities but doesn’t validate integrity beyond the hash.

Two-factor authentication (2FA) for package publishing adds some protection against account compromise, but again, this is at the publisher account level, not cryptographic signing of packages.

Projects like Sigstore and OpenSSF are exploring stronger solutions for package signing across ecosystems, but they’re not fully standard in npm yet.

Bottom Line:

Integrity of the downloaded package is verified against a cryptographic hash (so tampering in transit or registry compromise would be detected).

However, cryptographic proof of origin (like GPG signatures in apt/yum) is not part of npm’s default security model.

If you need that level of assurance, you would have to layer additional verification mechanisms yourself.