A log that cannot quietly change its mind

A signature proves who published an artifact. It does not prove they never published a different one. To close that gap the platform keeps a transparency log: an append-only record of every seal it issues, built as a Merkle tree in the style of RFC 6962, the same construction that underpins Certificate Transparency.

What “append-only” buys you

Each seal digest becomes a leaf in the tree. The tree head is summarised by a single root hash, and that root is itself signed in a checkpoint. Two properties follow, and they are the whole point:

Inclusion. For any entry, the log can produce a short proof that reconstructs the signed root from that leaf. If the proof checks, the entry is provably in the log the checkpoint commits to — the platform cannot show you an artifact and privately keep it out of the record.

Consistency. Given an older signed head and a newer one, the log can produce a proof that the new tree is an extension of the old — every entry the old head covered is still there, in the same place, and only new entries were appended. If that proof checks, the log cannot have rewritten history; it can only have grown.

The transparency page renders the shipped log and states both facts for the current head. Its build re-proves every inclusion proof and the extension from the prior head before the page may exist — a broken proof does not become a caveat on a live page, it stops the build.

Structure at build time, signature in your browser

There is a deliberate split in who checks what. The page proves the log’s structure at build time: leaf hashes match their proofs, proofs reconstruct the root, the new head extends the old one. It does not ask you to trust its word on the signature. That last check — is the checkpoint actually signed by the pinned root key — is re-run live, in your browser, by the workbench, against the same root the seal verifier uses.

The page says which is which, because conflating them would be a small dishonesty of exactly the kind the log exists to prevent. Structure is proven where the page is built; the signature belongs to the reader.

Why a small log still matters

The log is young and its tree is small. That is not a weakness to paper over — it is the honest state of a system that only records what it has actually published and refuses to pad the count. A log you can read end to end today is a log whose every claim you can check today. It grows one provable step at a time, and each step leaves a proof behind.