70 lines
3.4 KiB
Markdown
70 lines
3.4 KiB
Markdown
# ADR 0018: Sequence-free SSHSIGCHAIN authority protocol
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## Status
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Accepted for the generic core. The protocol is still pre-deployment and has no
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legacy compatibility requirement.
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## Context
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The first linked draft improved on a timestamp-sorted static bundle, but still
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made application profiles responsible for all key lifecycle semantics. It also
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included both a sequence counter and a parent hash, fixed one application
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profile for the whole chain, exposed every payload, and left rollback anchors
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outside the protocol model.
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That design would let applications fragment device/key behavior, made
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multi-profile least privilege awkward, and offered no standard way to disclose
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only selected profile data or compare independently anchored heads.
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## Decision
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SSHSIGCHAIN v1 is redesigned before deployment:
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- the trust tuple is `(chain ID, SSHSIG namespace, root public key)`;
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- parent hashes alone define order; there is no sequence number;
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- link identity hashes the signed outer bytes, not the signature encoding;
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- every link carries a mandatory public Authority v1 transition;
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- authority owns devices, keys, proof-of-possession, causal revocation,
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permission ceilings, delegation, and anchor policy;
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- applications use profile-ID-scoped, salted payload commitments and cannot
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mutate authority;
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- disclosures are transport additions which do not change a link or its hash;
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- authorized keys can sign head claims;
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- distinct head attesters and backend-neutral receipts are evaluated by
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separate weighted/required thresholds and required backend classes;
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- cached ancestors are never replaced by older heads and incomparable verified
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histories fail as forks; and
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- a policy-change head is witnessed under the preceding policy before the new
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policy governs descendants;
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- canonical `.sscb` bundles deterministically store records, separately
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discloseable payloads, claims, and receipts without embedding root trust;
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- JSONL is noncanonical human-facing interchange; and
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- distribution backends return untrusted bundle bytes through one interface,
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with a static HTTP profile that requires no server application.
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The generic core defines backend interfaces and deterministic policy behavior,
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not Nostr, HTTP, blockchain, or transparency-log clients. Those adapters belong
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outside `geth-keychain`. Backends provide evidence and discovery, not consensus.
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The generic protocol remains independent of geth transports. All geth
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node-to-node communication remains Iroh-only; SSH remains a trust and signature
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integration.
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## Consequences
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Device and key behavior is interoperable rather than reinvented in each
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profile. A verifier can validate current authority while withholding application
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data, but must report affected profile state as incomplete. Proofs of possession
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prevent an administrator from silently enrolling a key it does not control.
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Device ceilings and delegable permission sets constrain later amplification.
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The wire format is intentionally incompatible with every pre-deployment test
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draft. No migration parser or version alias is retained.
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Rollback protection still depends on persistent local accepted heads and the
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operator's anchor policy. A Nostr relay, mutable HTTP URL, blockchain, or
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transparency service has only the guarantees its receipt verifier and deployment
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actually establish. Canonical bundle conversion and verification exist, while
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automatic HTTP/Iroh fetching, durable accepted-head storage, and
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cross-implementation vectors remain follow-up work.
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