Sign and verify a blob end to end

This walks through signing an arbitrary byte string (a “blob”) keyless with k2gl/sigstore-sign and verifying the resulting bundle with k2gl/sigstore-verify.

Install

composer require k2gl/sigstore-sign k2gl/sigstore-verify

Both take a PSR-18 HTTP client and PSR-17 factories you supply.

Sign

Keyless signing exchanges an OIDC identity token for a short-lived Fulcio certificate, signs, and records the entry in Rekor — producing a bundle:

use K2gl\SigstoreSign\SigstoreSigner;

$signer = SigstoreSigner::keyless($fulcioClient, $rekorClient, $tsaClient);
$bundle = $signer->signArtifact($blob, $oidcToken);

file_put_contents('blob.sigstore.json', $bundle->toJson());

In CI you rarely construct the token by hand — k2gl/composer-attest-action wraps all of this for release artifacts.

Verify

use K2gl\Sigstore\SigstoreVerifier;
use K2gl\Sigstore\Bundle;
use K2gl\Sigstore\TrustedRoot;
use K2gl\Sigstore\IdentityPolicy;

$verifier = new SigstoreVerifier();

$verifier->verifyArtifact(
    Bundle::fromJson(file_get_contents('blob.sigstore.json')),
    $blob,
    TrustedRoot::fromSigstorePublicGood(),
    IdentityPolicy::sanRegex(
        '#^https://github\.com/your-org/your-repo/#',
        'https://token.actions.githubusercontent.com',
    ),
);

verifyArtifact throws on any failure — bad chain, missing transparency-log inclusion, wrong identity. If it returns, the blob’s provenance checks out.

The verifier passes the official sigstore-conformance suite, so bundles interoperate with cosign and other Sigstore clients. See the supply-chain overview.