Sigstore is an OpenSSF project, initiated by Google, Red Hat, and Purdue University, that provides a free public-good infrastructure for cryptographically signing software artifacts — container images, binaries, SBOMs, attestations — without the operational burden of managing long-lived private keys. Its founding insight is that the two hardest problems in code signing are key management (generating, protecting, distributing, rotating, and revoking signing keys across thousands of developers and CI pipelines) and signature discoverability (how does a verifier find and trust the correct public key for an artifact it has never seen before). Sigstore solves both by eliminating long-lived keys entirely: every signing operation generates a fresh ephemeral key pair, uses it once, discards the private key, and records the event in a public transparency log — replacing “do you trust this key?” with “do you trust this identity at this moment in time?”.
JWT (JSON Web Token), standardised in RFC 7519, is a compact, self-contained token format that encodes a set of claims — assertions about a subject, an issuer, an audience, and arbitrary application-defined attributes — as a JSON object, signs or encrypts it, and serialises the result as three base64url-encoded segments separated by dots: header.payload.signature. The header is a JSON object specifying the algorithm (alg) and optionally a key ID (kid) used to produce the signature. The payload is a JSON object containing the claims. The signature is computed over base64url(header) + "." + base64url(payload) using the algorithm declared in the header. The entire token is URL-safe, fits in an HTTP header or query parameter, and is self-describing — a verifier can locate the signing key, check the algorithm, verify the signature, and read the claims without any external lookup beyond fetching the issuer’s public key. This self-contained nature is what makes JWTs efficient at scale: unlike opaque tokens, which require a network call to the issuer’s introspection endpoint per verification, a JWT can be verified locally with a cached public key, making it suitable for high-throughput API gateways and distributed systems.
