Harden reusable keychain API

docs/architecture.md

@@ -352,13 +352,16 @@ are updated with signed `geth keychain admin-add` and `geth keychain
 admin-revoke` operations; `AdminKeyAdd` carries the public key material needed
 to reconstruct an OpenSSH `allowed_signers` view. `geth keychain verify` replays
 the log against the previously accepted admin-key view, mirroring the `git-skm`
-pattern of verifying key-registry changes from a prior trusted state. `geth
-keychain sync <node>` pulls keychain operations and signatures from an imported
-peer over Iroh and imports only operations with a valid OpenSSH signature from a
-currently trusted admin key over the canonical payload. See
-`docs/sigchain-keychain.md` for the detailed sigchain design. This is currently
-a pull-based signed operation log, not a CRDT or Keyhive-style convergent
-authority.
+pattern of verifying key-registry changes from a prior trusted state. The
+transport-neutral replay rules, application-specific signature namespaces,
+allowed-signers projection, and JSONL sigchain helpers live in `geth-keychain`
+so other applications can reuse the same identity-log model without depending
+on the daemon, SQLite, Iroh, or local control. `geth keychain sync <node>` pulls
+keychain operations and signatures from an imported peer over Iroh and imports
+only operations with a valid OpenSSH signature from a currently trusted admin
+key over the canonical payload. See `docs/sigchain-keychain.md` for the
+detailed sigchain design. This is currently a pull-based signed operation log,
+not a CRDT or Keyhive-style convergent authority.
 
 New devices can use the node enrollment flow instead of hand-editing keychain
 state. `geth node enroll request` creates a canonical, agent-key-signed request

docs/roadmap.md

@@ -332,6 +332,11 @@ resource-scoped capability decisions.
   - `[x]` `geth-keychain` exposes transport-neutral allowed-signers projection,
     replay verification with an injected verifier, and appendable JSONL
     sigchain encode/decode helpers for static hosting or alternate transports.
+  - `[x]` `geth-keychain` exposes `KeychainProfile` so non-geth applications
+    can use distinct signature namespaces and default principals.
+  - `[x]` `geth-keychain` exposes a `KeychainSignatureVerifier` trait so
+    callers can plug in OpenSSH, HSM, WebCrypto, service-side, or test
+    verification backends without daemon coupling.
   - `[x]` `docs/sigchain-keychain.md` documents the sigchain data model,
     verification algorithm, commands, and current security limits.
   - `[x]` Missing `ssh-keygen` or unavailable hardware keys produce clear

docs/sigchain-keychain.md

@@ -26,6 +26,19 @@ The durable log is `KeychainOp[]` plus `KeychainOpSignature[]`. Each operation
 has a deterministic canonical signing payload under the
 `geth.keychain.v1@geth.local` namespace.
 
+The namespace is part of a `KeychainProfile`. geth uses:
+
+- `geth.keychain.v1@geth.local`
+- `geth.node-enrollment-request.v1@geth.local`
+- default admin principal `admin`
+
+Other applications should create their own profile with explicit namespaces or
+`KeychainProfile::for_application("<app>", "<domain>")`. For example,
+`for_application("acme-notes", "example.com")` produces
+`acme-notes.keychain.v1@example.com`. This prevents signatures from one
+application's keychain from being replayed into another application's
+keychain.
+
 Important operation kinds:
 
 - `KeychainInit`
@@ -105,12 +118,31 @@ provide:
 
 - ordered or unordered `KeychainOp[]`
 - `KeychainOpSignature[]`
-- a signature verification callback
+- a `KeychainProfile`
+- a `KeychainSignatureVerifier`
 
-The callback is responsible for the cryptographic backend, such as
-`ssh-keygen -Y verify`, WebCrypto, an HSM, or a test verifier. The crate owns
-the replay order, bootstrap rule, previous-view authorization rule,
-`allowed_signers` projection, and reduced keychain view.
+The verifier is responsible for the cryptographic backend, such as
+`ssh-keygen -Y verify`, WebCrypto, an HSM, a service-side verifier, or a test
+verifier. The crate owns the replay order, bootstrap rule, profile namespace
+check, previous-view authorization rule, `allowed_signers` projection, and
+reduced keychain view.
+
+Minimal reusable Rust shape:
+
+```rust
+let profile = geth_keychain::KeychainProfile::for_application(
+    "acme-notes",
+    "example.com",
+)?;
+let entries = geth_keychain::decode_sigchain_jsonl(sigchain_text)?;
+let (ops, signatures) = geth_keychain::flatten_sigchain_entries(&entries);
+let report = geth_keychain::verify_sigchain_with_profile(
+    &ops,
+    &signatures,
+    &profile,
+    &my_verifier,
+);
+```
 
 ## Static Sigchain File