1.7 KiB
ADR 0018: Linked SSHSIGCHAIN v2
Status
Accepted for the new generic core and geth keychain profile. Legacy static sigchain publication is deprecated pending explicit v2 command migration.
Context
The prior static JSONL keychain flow replayed records after sorting mutable timestamps and used a downloaded allowed-signers projection to verify its own checkpoint. That permits self-bootstrapping trust and makes revocation, rollback, and fork semantics inadequate for a trust foundation.
Decision
Geth adopts SSHSIGCHAIN v2 as the replacement design:
- root trust is an explicit
(chain ID, profile, namespace, root key)tuple; - records are linearly ordered by sequence and linked by a digest over their signed content and SSHSIG signature;
- the initial root is only a genesis requirement, not a permanent bypass;
- profile authorization runs against the causally preceding state;
- key lifecycle is represented by causal add/revoke records, not timestamp validity fields; and
- payloads use deterministic binary codecs with a strict round-trip check.
The generic core is transport-independent. Geth continues using Iroh for all node-to-node communication; SSH remains an identity/signature integration and not a geth transport.
Consequences
The v2 core can be published and implemented by applications without importing geth's resource model. Geth's keychain profile is intentionally narrow and tested against self-bootstrap, fork, and backdated-revocation attacks.
Existing static v1 bundles cannot safely migrate in place. Operators must pin a new v2 trust tuple and create a new genesis chain. Head persistence and later witness/transparency support remain follow-up work; neither is implied by a single signed checkpoint.