# Manifest signing migration

The installed launcher population currently pins the 3072-bit RSA public key in
`ptlinux/launcher-update-public.pem`. Release scripts also support OpenSSL
Ed25519 keys, but changing the Gitea secret before clients receive the new
public key would make all metadata unverifiable.

Use this staged migration when Ed25519 is adopted:

1. Generate the Ed25519 key pair offline. Keep the private key out of the
   repository and record the public-key fingerprint through the normal release
   review process.
2. Publish a normal RSA-signed transition release. That immutable archive adds
   the Ed25519 public key and updater support, while its channel manifest still
   verifies with the RSA key already installed on clients.
3. Verify the transition release from a clean pre-transition installation on
   both stable and prerelease channel paths. Confirm rollback still verifies old
   RSA-signed historical manifests.
4. Keep `manifest.json.sig` RSA-signed while enough installations move to the
   transition release. If dual signatures are introduced, upload the Ed25519
   signature under a separate filename; never change the meaning of the legacy
   `.sig` asset for old clients.
5. Publish a second RSA-signed release that makes the updater choose signatures
   by an authenticated algorithm and key identifier, and bundles a keyring with
   both public keys. Its minimum updater compatibility must prevent an older
   verifier from trusting metadata it cannot authenticate.
6. Replace the protected Actions signing secret only after the keyring release
   is deployed and measured. Exercise stable discovery, prerelease discovery,
   remote rollback, withdrawal publication, and tamper rejection with Ed25519.
7. Retire RSA verification in a later release. Retain the old public key for
   immutable historical rollback metadata until those releases are outside the
   supported rollback window.

At every stage, a failed or incorrectly signed tag remains immutable. Correct
the pipeline and publish the next semantic version rather than replacing assets.