DESIGN.md

@@ -123,9 +123,11 @@ means a future route cannot pass a string where a proof belongs.
 
 `revoke <agent>` with no end time is permanent: the enrolled public key is
 cleared and the identity stays dead until someone bootstraps a fresh secret and
-rekeys (or re-enrols). `reinstate` alone lifts the ban flags but does **not**
+calls `enrol_rekey` (then `reinstate` if still banned). `enrol` will not work —
-restore the compromised key — that was the footgun. `revoke <agent> --until
+the agent row still exists — and would only burn the seed. `reinstate` alone
-<unix>` is a pause that keeps the key, and it lapses on its own.
+lifts the ban flags but does **not** restore the compromised key — that was the
+footgun. `revoke <agent> --until <unix>` is a pause that keeps the key, and it
+lapses on its own.
 
 The distinction matters because the two failure modes are different. A key
 compromise wants death — a lapsing revocation would hand the attacker back in
@@ -134,10 +136,17 @@ wrong moment. A noisy neighbour or a holiday wants a pause, and re-enrolling for
 that would destroy the audit history that says it was deliberate.
 
 Revoking kills live sessions, drops outstanding challenges, and invalidates
-unused view codes, so a revocation that races an in-flight authentication
+unused view codes. Rekey invalidates codes the same way: rotating a key must
-cannot be overtaken by it, and a pre-issued code cannot mint a fresh human
+close every door the old key could open.
-session after the agent is suspended or dead. Rekey invalidates codes the same
+
-way: rotating a key must close every door the old key could open.
+A narrow check-then-insert race can still insert a session or code after the
+revoke/rekey statement has run. The choke point is `sessions.resolve`: every
+use re-checks that the agent is not revoked, still has a live key, and that
+the session fingerprint (when present — always for agent sessions, and for
+human_via_agent sessions minted with a fingerprint) matches the current key
+epoch. View codes store the issuing fingerprint and refuse redeem after rekey
+or key wipe. That is what makes revocation overtake in-flight
+verify/issue/redeem, not the first-pass invalidation alone.
 
 ### Existing controls stay
 
@@ -195,9 +204,15 @@ history, forges replacements, and rebuilds the chain — `verify_chain` passes.
 So the head digest also gets **signed checkpoints**, by an enrolled agent whose
 private key the database does not contain. `verify-chain` runs both checks, and
 the rewrite is caught by the signature the attacker cannot produce. A forged
-checkpoint fails signature verification, a checkpoint from a stranger is refused
+checkpoint fails signature verification, and a checkpoint from a stranger is
-at signing time, and a rekey invalidates every earlier checkpoint — which is
+refused at signing time.
-correct, and says so rather than failing quietly.
+
+Public keys are kept in an append-only `agent_keys` history. Revoke and rekey
+*retire* a key rather than destroy it, so honest pre-compromise checkpoints and
+off-box anchors stay verifiable against the fingerprint they name. Checkpoints
+timestamped after a key's `retired_at` are flagged (not failed). Prefer a
+**dedicated checkpoint-signer identity** that is never a working agent, so a
+routine agent compromise-revoke does not touch the tip-signing key at all.
 
 What this still does not do is survive an attacker who can also delete the
 checkpoints, because they live in the same database. Set `anchor_path` /
@@ -216,7 +231,7 @@ because the review looked for it.
 
 ## Status
 
-106 passing tests, and two hardening passes that closed real defects. The worst were
+158 passing tests, and two hardening passes that closed real defects. The worst were
 concurrency: one-time codes were redeemable repeatedly (753 sessions from 200
 codes under load), and a bootstrap secret could enrol more than one key. Those
 are now atomic compare-and-set operations, each covered by a test that races
@@ -229,7 +244,7 @@ sessions mintable from a bare agent name, no revocation operation at all, an
 unkeyed chain that a database-level attacker could rebuild, and SQLite without
 a busy timeout.
 
-Leora's contracted prod pass (Quarry 18a5d762) closed three remaining review blockers on this branch: rekey no longer un-revokes, dual-bootstrap enrol is exactly-one under race, and redeem rate limits are per-agent (anonymous fails isolated from success). Off-box checkpoint tip publish/verify ships when `anchor_path` / `SIGIL_ANCHOR` is set. SealedStore / `SIGIL_SEAL_PASS` seals the DB file with AES-256-GCM (incremental path short of SQLCipher). Independent review and platform glue remain.
+Leora's contracted prod pass (Quarry 18a5d762) closed three remaining review blockers on this branch: rekey no longer un-revokes, dual-bootstrap enrol is exactly-one under race, and redeem rate limits are per-agent (anonymous fails isolated from success). Off-box checkpoint tip publish/verify ships when `anchor_path` / `SIGIL_ANCHOR` is set. SealedStore / `SIGIL_SEAL_PASS` seals the DB file with AES-256-GCM (incremental path short of SQLCipher). Independent review returned GO-WITH-FIXES; R1–R8/R11 fixes on this branch. Platform glue remains off.
 
 **Still not production ready**, and the reason is not a to-do list:
 
@@ -241,7 +256,8 @@ Leora's contracted prod pass (Quarry 18a5d762) closed three remaining review blo
   rewrite that in-DB checkpoints alone would miss after deletion. Leave it unset
   and the tip stays in-DB only.
 - **The service is unwritten.** TLS, CSRF, transport, routes. DB file seal is
-  available (`SealedStore`); SQLCipher page-level encryption is not.
+  available (`SealedStore`, plaintext working copy `0600`); SQLCipher
+  page-level encryption is deferred (not yet available).
 - **Rate limits are per-process**, so N processes means N times the quota.
 - **No key recovery.** Rotate and old sessions die. Deliberate.
 - **Humans remain unattributable** to themselves, which is accepted and is a
@@ -251,11 +267,27 @@ The tests show the logic is correct. They do not make it safe.
 
 ## Next
 
-1. Independent security review before this guards anything real. Two hardening
+1. ~~Independent security review~~ — independent review returned GO-WITH-FIXES
-   passes made it reviewable; neither substituted for one.
+   (tip c0027bb); fix PRs for R1–R8/R11 landed on `sigil-initial`. Platform glue
+   remains off until integration review. See `docs/PROD_RUNBOOK.md`.
 2. ~~Anchor the checkpoint head digest outside the database~~ — done via
    `Store(..., anchor_path=)` / `SIGIL_ANCHOR` (signed tip file + `.log`).
+   **Prod must set it** (see runbook).
 3. Secret broker on top — scoped, short-lived leases bound to a key fingerprint.
    Its issuance and redemption logs *are* the work-attestation substrate, so it
    is the natural second piece.
 4. Deprecate passcode login across the platform, then rotate live credentials.
+
+### Info / follow-ups (no code change required yet)
+
+- **R9 — `issue_agent_session`:** library helper mints `agent:act` from a name
+  after the caller claims to have verified. Keep internal; integration must
+  never mint from headers/names. Consider renaming to `_issue_agent_session`.
+- **R10 — challenge domain separation:** signatures currently cover
+  `nonce.encode()` with no context prefix. Adding
+  `b"sigil-challenge-v1\0" + nonce` is not backward-compatible with in-flight
+  challenges; schedule with a protocol version bump (follow-up).
+- **R12 — multi-process rate limits:** quotas are per-`Store` / per-process.
+  Single writer until a shared limiter exists (documented in README + runbook).
+- **R13 — opt-in anchor:** without `SIGIL_ANCHOR`, deleting in-DB checkpoints
+  allows silent history rewrite. Runbook requires the anchor on separate storage.

README.md

@@ -55,7 +55,7 @@ python3 sigil.py sweep                                # prune stale rows
 python3 -m unittest discover -s tests -v
 ```
 
-130 tests. They cover the refusals, not just the happy paths: replayed
+158 tests. They cover the refusals, not just the happy paths: replayed
 signatures, wrong keys, expired nonces, single-use codes, scope escalation, and
 the invariant below. `test_hardening.py`, `test_production.py`, `test_anchor.py` and
 `test_sealed.py` have one test per defect found in review, so any of them
@@ -137,7 +137,9 @@ Still open, and these are the reasons not to ship it yet:
 - **The service around this is unwritten.** TLS, CSRF, session transport and the
   HTTP routes. DB encryption at rest is available via `SealedStore` /
   `SIGIL_SEAL_PASS` (AES-256-GCM file seal; not SQLCipher page-level). The
-  library refuses to mint authority from a name, so a route that forgets to
+  plaintext working copy is mode `0600` in a private temp dir while open;
+  SQLCipher remains deferred for hostile co-resident hosts. The library
+  refuses to mint authority from a name, so a route that forgets to
   authenticate fails closed, but that is only as good as the integration.
 - **Off-box anchor is opt-in.** Set `SIGIL_ANCHOR` (or `Store(..., anchor_path=)`)
   and every checkpoint also writes a signed tip outside the SQLite file.
@@ -157,3 +159,8 @@ The tests assert the logic is correct. They do not make it safe.
 
 `DESIGN.md` — the design page: rationale, flows, session stamps, the invariant
 and its reasoning, and what is deferred.
+
+`docs/PROD_RUNBOOK.md` — production checklist: require `SIGIL_SEAL_PASS` and
+`SIGIL_ANCHOR` on separate storage, verify-chain alerts, integration sharp edges.
+
+`requirements.txt` — `cryptography>=44.0.1,<45`; see `requirements.lock.txt` / `constraints.txt`.

constraints.txt

@@ -0,0 +1,3 @@
+# Exact pin matching requirements.lock.txt floor. Use with:
+#   pip install -r requirements.txt -c constraints.txt
+cryptography==44.0.1

docs/PROD_RUNBOOK.md

@@ -0,0 +1,46 @@
+# Sigil production runbook
+
+Short checklist before Sigil guards anything real. Library-only today — do **not**
+enable platform glue until an integration review covers session minting.
+
+## Required environment
+
+| Variable | Purpose | Notes |
+|----------|---------|--------|
+| `SIGIL_DB` | Path to the store file | Prefer a dedicated volume; backups are sensitive (roster + audit). |
+| `SIGIL_SEAL_PASS` | AES-256-GCM seal passphrase | **Required in prod.** ≥12 chars. Without it the DB file is cleartext on disk. Seal-on still uses a plaintext `0600` working copy while the process is open — not SQLCipher. |
+| `SIGIL_ANCHOR` | Off-box signed tip path | **Required in prod.** Must be on storage **separate** from `SIGIL_DB` (different volume/host). Every checkpoint publishes here; `verify_external_anchors` / `verify-chain` must alert on failure. |
+
+Optional: agent private keys stay **off** the platform host whenever possible; checkpoint signer key preferably offline.
+
+## Dedicated checkpoint-signer identity
+
+Enrol a separate agent id used **only** for `checkpoint` / `publish_anchor`
+(for example `sigil-checkpoint`). Do not use a working agent as the tip signer:
+compromising and permanently revoking that agent would otherwise retire its key
+(history still verifies, but ops alerting on "key retired" gets noisy). Never
+store the checkpoint signer's private key in the Sigil DB — public history only.
+
+## Ops loop
+
+1. Open with seal + anchor configured (CLI respects the env vars above).
+2. Periodically run chain verify **and** external-anchor verify; page on failure.
+3. After permanent revoke (compromise): bootstrap + `enrol_rekey`, then `reinstate`. Reinstate alone does not restore a wiped key.
+4. Single writer process until a shared rate-limit store exists (in-process quotas multiply across processes).
+
+## Integration sharp edges (do not ignore)
+
+- Never mint `issue_agent_session` from a client-supplied name or header. Only after a verified challenge-response. Prefer keeping that helper internal to verified paths.
+- Human view codes are ~40 bits; keep TTL short; never log raw codes (already hashed in audit).
+- Challenge signatures today sign the raw nonce (no domain separation). Changing the signed payload needs a coordinated version bump — tracked as a follow-up, not a silent break.
+
+## Deferred
+
+- SQLCipher / page-level encryption for multi-tenant co-resident hosts.
+- Domain-separated challenge payloads (`sigil-challenge-v1` prefix) — backward-incompatible without a protocol version.
+- Shared cross-process rate limiter.
+
+## Dependencies
+
+Install with `pip install -r requirements.txt -c constraints.txt`
+(or `--require-hashes -r requirements.lock.txt`). Floor is `cryptography>=44.0.1`.

requirements.lock.txt

@@ -0,0 +1,13 @@
+# Hash-pinned lock for Sigil runtime crypto deps.
+# Install: pip install --require-hashes -r requirements.lock.txt
+# Floor cryptography==44.0.1 addresses CVE-2024-12797 in older wheels.
+
+cryptography==44.0.1 \
+    --hash=sha256:53f23339864b617a3dfc2b0ac8d5c432625c80014c25caac9082314e9de56f41
+
+cffi==2.1.1 \
+    --hash=sha256:a931079504ecc49efed7744c476a5c343a92fabf66dec2db95edb1b2fdc770e2
+
+pycparser==3.0 \
+    --hash=sha256:b727414169a36b7d524c1c3e31839a521725078d7b2ff038656844266160a992
+

requirements.txt

@@ -0,0 +1,5 @@
+# Runtime dependency for Ed25519 + AES-GCM (SealedStore / optional key files).
+# Lower bound 44.0.1: older 43.x/44.0.0 wheels ship OpenSSL affected by
+# CVE-2024-12797 (GHSA-79v4-65xg-pq4g). Upper bound <45 keeps upgrades deliberate.
+# For hash-pinned install see requirements.lock.txt.
+cryptography>=44.0.1,<45

sigil/identity.py

@@ -78,6 +78,10 @@ def enrol(
     _validate_agent_id(agent)
     if not store.allow(f"enrol:{agent}"):
         raise errors.RateLimited(f"too many enrolment attempts for {agent}")
+    # Already enrolled (e.g. after permanent revoke): refuse *before* spending
+    # the seed so ops following a wrong "re-enrol" path do not burn it.
+    if store.get_agent(agent) is not None:
+        raise errors.EnrolmentFailed(f"{agent} is already enrolled; use enrol_rekey")
     # Spend the secret first so a burned secret cannot be retried. The agent
     # row insert below is INSERT OR IGNORE: if two secrets race for the same
     # unenrolled agent, exactly one put_agent wins and the loser fails closed
@@ -295,6 +299,10 @@ def enrol_rekey(store: Store, agent: str, public_b64: str, secret: str) -> str:
         raise errors.UnknownAgent(f"{agent} is revoked")
     owner = store.spend_bootstrap(_hash_secret(secret))
     if owner != agent:
+        # Rate-limit only failed attempts so junk cannot burn the ops path, and
+        # use a dedicated rekey: bucket so exhausting enrol: cannot lock rekey.
+        if not store.allow(f"rekey:{agent}"):
+            raise errors.RateLimited(f"too many rekey attempts for {agent}")
         raise errors.EnrolmentFailed("bootstrap secret invalid or already spent")
     public = keys.import_public_b64(public_b64)
     fingerprint = keys.fingerprint(public)

sigil/sealed.py

@@ -11,6 +11,11 @@ working copy is plaintext in memory / a temp file while open). It is a real
 working seal: the file on disk is ciphertext, and tests assert a stolen seal
 has no SQLite header and no recoverable agent rows without the passphrase.
 
+The plaintext working copy is created mode 0600 inside a private temp dir.
+SQLCipher (or equivalent page-level encryption) remains a deferred prod
+follow-up for multi-tenant / hostile co-resident hosts — never treat seal-on
+as "encrypted DB" while the process is running.
+
 Format on disk (version 1):
 
     b"SIGILSEAL1" + 16-byte salt + 12-byte nonce + AESGCM(ciphertext)
@@ -83,6 +88,30 @@ def is_sealed_file(path: str) -> bool:
         return handle.read(len(MAGIC)) == MAGIC
 
 
+def _write_private_file(path: str, data: bytes) -> None:
+    """Write `data` to `path` with mode 0600, fsync, unlink on failure."""
+    flags = os.O_WRONLY | os.O_CREAT | os.O_TRUNC
+    fd = os.open(path, flags, 0o600)
+    try:
+        with os.fdopen(fd, "wb") as handle:
+            fd = -1  # ownership transferred
+            handle.write(data)
+            handle.flush()
+            os.fsync(handle.fileno())
+        os.chmod(path, 0o600)
+    except Exception:
+        if fd >= 0:
+            try:
+                os.close(fd)
+            except OSError:
+                pass
+        try:
+            os.unlink(path)
+        except OSError:
+            pass
+        raise
+
+
 class SealedStore(Store):
     """Store whose on-disk file is AES-GCM sealed.
 
@@ -107,6 +136,8 @@ class SealedStore(Store):
         self.seal_path = path
         self._passphrase = passphrase
         self._tmpdir = tempfile.TemporaryDirectory(prefix="sigil-seal-")
+        # TemporaryDirectory is already 0700; pin the dir mode explicitly.
+        os.chmod(self._tmpdir.name, 0o700)
         self._plain_path = os.path.join(self._tmpdir.name, "store.db")
         if os.path.exists(path):
             with open(path, "rb") as handle:
@@ -117,9 +148,16 @@ class SealedStore(Store):
                     "refusing to treat a cleartext DB as sealed"
                 )
             plain = unseal_bytes(blob, passphrase)
-            with open(self._plain_path, "wb") as handle:
+            _write_private_file(self._plain_path, plain)
-                handle.write(plain)
+        else:
+            # Touch an empty 0600 file so SQLite does not create a world-readable DB.
+            _write_private_file(self._plain_path, b"")
         super().__init__(self._plain_path, anchor_path=anchor_path)
+        # Re-pin after SQLite open (WAL/SHM sidecars inherit umask otherwise).
+        try:
+            os.chmod(self._plain_path, 0o600)
+        except OSError:
+            pass
 
     def flush(self) -> str:
         """Checkpoint WAL, read plaintext bytes, write sealed blob to seal_path."""
@@ -130,14 +168,24 @@ class SealedStore(Store):
             dest_path = os.path.join(self._tmpdir.name, "export.db")
             if os.path.exists(dest_path):
                 os.unlink(dest_path)
+            # Pre-create 0600 so SQLite backup does not leave a world-readable export.
+            _write_private_file(dest_path, b"")
             dest = sqlite3.connect(dest_path)
             try:
                 self.conn.backup(dest)
                 dest.commit()
             finally:
                 dest.close()
+            try:
+                os.chmod(dest_path, 0o600)
+            except OSError:
+                pass
             with open(dest_path, "rb") as handle:
                 plain = handle.read()
+            try:
+                os.unlink(dest_path)
+            except OSError:
+                pass
             blob = seal_bytes(plain, self._passphrase)
             directory = os.path.dirname(os.path.abspath(self.seal_path))
             if directory:

sigil/sessions.py

@@ -105,9 +105,16 @@ class GrantedCode:
     agent session (issue_code) or a valid code (redeem_code).
     """
 
-    __slots__ = ("agent", "scopes", "ttl", "_sigil_internal")
+    __slots__ = ("agent", "scopes", "ttl", "fingerprint", "_sigil_internal")
 
-    def __init__(self, agent: str, scopes: List[str], ttl: int, _internal=None):
+    def __init__(
+        self,
+        agent: str,
+        scopes: List[str],
+        ttl: int,
+        _internal=None,
+        fingerprint: Optional[str] = None,
+    ):
         if _internal is not _ISSUER:
             raise errors.SigilError(
                 "GrantedCode cannot be constructed directly; it comes from"
@@ -116,6 +123,7 @@ class GrantedCode:
         self.agent = agent
         self.scopes = list(scopes)
         self.ttl = ttl
+        self.fingerprint = fingerprint
         self._sigil_internal = _internal
 
     def __repr__(self) -> str:
@@ -151,6 +159,7 @@ def issue_view_session(store: Store, grant: "GrantedCode") -> dict:
         granted,
         expires,
         granted_by=agent,
+        fingerprint=grant.fingerprint,
     )
     store.record(
         "session.issued",
@@ -176,7 +185,14 @@ def issue_view_session(store: Store, grant: "GrantedCode") -> dict:
 
 
 def resolve(store: Store, token: str) -> dict:
-    """Look up a session and reject it if revoked or expired."""
+    """Look up a session and reject it if revoked, expired, or the agent died.
+
+    The session row alone is not enough: an in-flight verify/issue_code can
+    insert a session or code after revoke/rekey has already run. Re-check the
+    agent on every resolve so a race-surviving bearer cannot keep acting.
+    """
+    from . import identity as _identity
+
     row = store.get_session(hash_token(token))
     if row is None:
         raise errors.SessionUnknown("no such session")
@@ -184,6 +200,24 @@ def resolve(store: Store, token: str) -> dict:
         raise errors.SessionExpired("session revoked")
     if time.time() >= row["expires_at"]:
         raise errors.SessionExpired("session expired")
+
+    agent = row["on_behalf_of"]
+    agent_row = store.get_agent(agent)
+    if agent_row is None or _identity.is_revoked(agent_row):
+        raise errors.SessionExpired("agent revoked")
+    if not _identity.has_live_key(agent_row):
+        raise errors.SessionExpired("agent has no live key")
+    # Every session that carries a fingerprint is bound to that key epoch.
+    # After rekey, race-surviving agent:act *and* human_via_agent bearers die
+    # even if revoke_sessions missed them (N7).
+    sess_fp = row["fingerprint"] or ""
+    live_fp = agent_row["fingerprint"] or ""
+    if sess_fp or row["kind"] == AGENT:
+        # Agent sessions always require a matching fingerprint; human sessions
+        # require a match whenever a fingerprint was recorded at mint time.
+        if not sess_fp or sess_fp != live_fp:
+            raise errors.SessionExpired("session key epoch no longer current")
+
     return {
         "token": token,
         "kind": row["kind"],

sigil/store.py

@@ -36,6 +36,20 @@ CREATE TABLE IF NOT EXISTS agents (
     revoked_reason TEXT
 );
 
+-- Append-only public-key history. Revoke and rekey *retire* a key instead of
+-- destroying it, so historical checkpoints and off-box anchors stay verifiable.
+-- Never stores private keys.
+CREATE TABLE IF NOT EXISTS agent_keys (
+    agent          TEXT NOT NULL,
+    fingerprint    TEXT NOT NULL,
+    pubkey         BLOB NOT NULL,
+    active_from    INTEGER NOT NULL,
+    retired_at     INTEGER,
+    retired_reason TEXT,
+    PRIMARY KEY (agent, fingerprint)
+);
+CREATE INDEX IF NOT EXISTS agent_keys_agent ON agent_keys(agent, active_from);
+
 -- Enrolment bootstrap secrets. Spent secrets are deleted, not marked, so a
 -- spent secret cannot be replayed even if the table is read.
 CREATE TABLE IF NOT EXISTS bootstrap (
@@ -77,7 +91,11 @@ CREATE TABLE IF NOT EXISTS codes (
     redeem_expires_at INTEGER NOT NULL,  -- short: the code is a key
     view_ttl         INTEGER NOT NULL,   -- the door opens a full hour, but only
                                         -- once the key is used
-    used_at         INTEGER
+    used_at         INTEGER,
+    -- Fingerprint of the agent key at issue time. Redeem refuses if the agent
+    -- has since rekeyed (or been wiped), so an in-flight issue_code cannot
+    -- outlive a revoke/rekey that lands before put_code commits.
+    fingerprint     TEXT
 );
 
 -- Append-only, hash-chained audit log. The chain is what makes this an
@@ -130,6 +148,9 @@ RATE_LIMITS = {
     "challenge": (30, 60),      # 30 per 60s
     "verify": (60, 60),
     "enrol": (10, 300),
+    # Separate from enrol: junk pre-auth enrol_rekey must not lock out ops
+    # rotating a compromised agent during incident response.
+    "rekey": (10, 300),
     "code_issue": (20, 300),
     "code_redeem": (20, 60),
     "code_redeem_fail": (10, 300),
@@ -217,6 +238,22 @@ class Store:
             self.conn.execute(
                 "UPDATE codes SET view_ttl = 3600 WHERE view_ttl IS NULL"
             )
+        code_cols = {
+            row["name"] for row in self.conn.execute("PRAGMA table_info(codes)")
+        }
+        if "fingerprint" not in code_cols:
+            self.conn.execute("ALTER TABLE codes ADD COLUMN fingerprint TEXT")
+        # Backfill agent_keys from current agents rows (live or wiped-empty skipped).
+        for row in self.conn.execute(
+            "SELECT agent, pubkey, fingerprint, enrolled_at FROM agents"
+            " WHERE fingerprint IS NOT NULL AND fingerprint != ''"
+            " AND length(pubkey) = 32"
+        ):
+            self.conn.execute(
+                "INSERT OR IGNORE INTO agent_keys"
+                " (agent, fingerprint, pubkey, active_from) VALUES (?, ?, ?, ?)",
+                (row["agent"], row["fingerprint"], row["pubkey"], row["enrolled_at"]),
+            )
         self.conn.commit()
 
     def close(self) -> None:
@@ -253,12 +290,19 @@ class Store:
         which preserves revocation columns.
         """
         with self._write_lock:
+            now = int(time.time())
             cur = self.conn.execute(
                 "INSERT OR IGNORE INTO agents"
                 " (agent, pubkey, fingerprint, enrolled_at)"
                 " VALUES (?, ?, ?, ?)",
-                (agent, pubkey, fingerprint, int(time.time())),
+                (agent, pubkey, fingerprint, now),
             )
+            if cur.rowcount == 1:
+                self.conn.execute(
+                    "INSERT OR IGNORE INTO agent_keys"
+                    " (agent, fingerprint, pubkey, active_from) VALUES (?, ?, ?, ?)",
+                    (agent, fingerprint, pubkey, now),
+                )
             self.conn.commit()
             return cur.rowcount == 1
 
@@ -270,10 +314,33 @@ class Store:
         used to un-revoke. An UPDATE of only the key columns keeps the ban intact.
         """
         with self._write_lock:
+            now = int(time.time())
+            prev = self.conn.execute(
+                "SELECT pubkey, fingerprint, enrolled_at FROM agents WHERE agent = ?",
+                (agent,),
+            ).fetchone()
             cur = self.conn.execute(
                 "UPDATE agents SET pubkey = ?, fingerprint = ? WHERE agent = ?",
                 (pubkey, fingerprint, agent),
             )
+            if cur.rowcount == 1 and prev is not None:
+                old_fp = prev["fingerprint"] or ""
+                if old_fp and len(prev["pubkey"] or b"") == 32:
+                    self.conn.execute(
+                        "INSERT OR IGNORE INTO agent_keys"
+                        " (agent, fingerprint, pubkey, active_from) VALUES (?, ?, ?, ?)",
+                        (agent, old_fp, prev["pubkey"], prev["enrolled_at"] or now),
+                    )
+                    self.conn.execute(
+                        "UPDATE agent_keys SET retired_at = ?, retired_reason = ?"
+                        " WHERE agent = ? AND fingerprint = ? AND retired_at IS NULL",
+                        (now, "rekey", agent, old_fp),
+                    )
+                self.conn.execute(
+                    "INSERT OR IGNORE INTO agent_keys"
+                    " (agent, fingerprint, pubkey, active_from) VALUES (?, ?, ?, ?)",
+                    (agent, fingerprint, pubkey, now),
+                )
             self.conn.commit()
             return cur.rowcount == 1
 
@@ -285,20 +352,39 @@ class Store:
         """Suspend an agent. `until` of None is permanent.
 
         A permanent revoke clears the enrolled public key so `reinstate` alone
-        cannot restore a compromised identity — ops must bootstrap + rekey
+        cannot restore a compromised identity — ops must bootstrap + enrol_rekey
-        (or enrol) before the agent can authenticate again. Timed suspension
+        before the agent can authenticate again. Timed suspension keeps the
-        keeps the key: when the pause lapses, the same key works.
+        key: when the pause lapses, the same key works.
 
         Returns how many live sessions were killed.
         """
         with self._write_lock:
             if until is None:
-                # Permanent: wipe key material. Empty fingerprint means
+                # Permanent: retire the public key into agent_keys (so historical
-                # "pending rekey" — see identity.has_live_key.
+                # checkpoints stay verifiable), then wipe the live slot.
+                now = int(time.time())
+                prev = self.conn.execute(
+                    "SELECT pubkey, fingerprint, enrolled_at FROM agents WHERE agent = ?",
+                    (agent,),
+                ).fetchone()
+                if prev is not None:
+                    old_fp = prev["fingerprint"] or ""
+                    if old_fp and len(prev["pubkey"] or b"") == 32:
+                        self.conn.execute(
+                            "INSERT OR IGNORE INTO agent_keys"
+                            " (agent, fingerprint, pubkey, active_from)"
+                            " VALUES (?, ?, ?, ?)",
+                            (agent, old_fp, prev["pubkey"], prev["enrolled_at"] or now),
+                        )
+                        self.conn.execute(
+                            "UPDATE agent_keys SET retired_at = ?, retired_reason = ?"
+                            " WHERE agent = ? AND fingerprint = ? AND retired_at IS NULL",
+                            (now, reason or "permanent revoke", agent, old_fp),
+                        )
                 self.conn.execute(
                     "UPDATE agents SET revoked_at = ?, revoked_until = ?, revoked_reason = ?,"
                     " pubkey = ?, fingerprint = ? WHERE agent = ?",
-                    (int(time.time()), until, reason, b"", "", agent),
+                    (now, until, reason, b"", "", agent),
                 )
             else:
                 self.conn.execute(
@@ -335,8 +421,8 @@ class Store:
         with self._write_lock:
             now = int(time.time())
             self.conn.execute(
-                "UPDATE bootstrap SET spent_at = ? WHERE agent = ? AND spent_at IS NULL",
+                "DELETE FROM bootstrap WHERE agent = ? AND spent_at IS NULL",
-                (now, agent),
+                (agent,),
             )
             self.conn.execute(
                 "INSERT INTO bootstrap (secret_hash, agent, created_at) VALUES (?, ?, ?)",
@@ -345,7 +431,7 @@ class Store:
             self.conn.commit()
 
     def clear_bootstrap_for_agent(self, agent: str, *, keep_hash: Optional[str] = None) -> int:
-        """Spend (or delete) every unspent bootstrap secret for an agent.
+        """Delete every unspent bootstrap secret for an agent.
 
         After a successful enrol / enrol_rekey, leftover seeds must not remain
         usable. keep_hash, when set, is left alone (already consumed by CAS).
@@ -353,14 +439,14 @@ class Store:
         with self._write_lock:
             if keep_hash is None:
                 cur = self.conn.execute(
-                    "UPDATE bootstrap SET spent_at = ? WHERE agent = ? AND spent_at IS NULL",
+                    "DELETE FROM bootstrap WHERE agent = ? AND spent_at IS NULL",
-                    (int(time.time()), agent),
+                    (agent,),
                 )
             else:
                 cur = self.conn.execute(
-                    "UPDATE bootstrap SET spent_at = ? WHERE agent = ? AND spent_at IS NULL"
+                    "DELETE FROM bootstrap WHERE agent = ? AND spent_at IS NULL"
                     " AND secret_hash != ?",
-                    (int(time.time()), agent, keep_hash),
+                    (agent, keep_hash),
                 )
             self.conn.commit()
             return cur.rowcount
@@ -368,23 +454,26 @@ class Store:
     def spend_bootstrap(self, secret_hash: str) -> Optional[str]:
         """Atomically consume an enrolment secret. Returns the agent or None.
 
-        Compare-and-set: the UPDATE only matches an unspent row, so exactly one
+        Compare-and-set then delete: exactly one concurrent caller can win, and
-        concurrent caller can win. Check-then-update would let a secret enrol
+        the spent row is removed so a table dump cannot offline-crack a
-        more than one key.
+        low-entropy custom secret. Matches the schema comment.
         """
         with self._write_lock:
+            row = self.conn.execute(
+                "SELECT agent FROM bootstrap WHERE secret_hash = ? AND spent_at IS NULL",
+                (secret_hash,),
+            ).fetchone()
+            if row is None:
+                return None
+            agent = row["agent"]
             cur = self.conn.execute(
-                "UPDATE bootstrap SET spent_at = ? WHERE secret_hash = ?"
+                "DELETE FROM bootstrap WHERE secret_hash = ? AND spent_at IS NULL",
-                " AND spent_at IS NULL",
+                (secret_hash,),
-                (int(time.time()), secret_hash),
             )
             self.conn.commit()
             if cur.rowcount != 1:
                 return None
-            row = self.conn.execute(
+            return agent
-                "SELECT agent FROM bootstrap WHERE secret_hash = ?", (secret_hash,)
-            ).fetchone()
-            return row["agent"] if row else None
 
     # -- nonces ------------------------------------------------------------
     def put_nonce(self, nonce: str, agent: str, expires_at: int) -> None:
@@ -492,10 +581,11 @@ class Store:
         scopes: List[str],
         redeem_expires_at: int,
         view_ttl: int,
+        fingerprint: Optional[str] = None,
     ) -> None:
         self._exec(
             "INSERT INTO codes (code_hash, agent, scopes, issued_at, redeem_expires_at,"
-            " view_ttl) VALUES (?, ?, ?, ?, ?, ?)",
+            " view_ttl, fingerprint) VALUES (?, ?, ?, ?, ?, ?, ?)",
             (
                 code_hash,
                 agent,
@@ -503,6 +593,7 @@ class Store:
                 int(time.time()),
                 redeem_expires_at,
                 view_ttl,
+                fingerprint,
             ),
         )
 
@@ -510,14 +601,17 @@ class Store:
         return self._one("SELECT * FROM codes WHERE code_hash = ?", (code_hash,))
 
     def claim_code(self, code_hash: str) -> bool:
-        """Consume a one-time code exactly once. False if already used.
+        """Consume a one-time code exactly once. False if already used or expired.
 
-        Atomic, so a code cannot mint two sessions under a race.
+        Atomic CAS includes the expiry predicate so a race at the TTL boundary
+        cannot mint a session slightly after redeem_expires_at.
         """
         with self._write_lock:
+            now = int(time.time())
             cur = self.conn.execute(
-                "UPDATE codes SET used_at = ? WHERE code_hash = ? AND used_at IS NULL",
+                "UPDATE codes SET used_at = ? WHERE code_hash = ? AND used_at IS NULL"
-                (int(time.time()), code_hash),
+                " AND redeem_expires_at > ?",
+                (now, code_hash, now),
             )
             self.conn.commit()
             return cur.rowcount == 1
@@ -646,7 +740,26 @@ class Store:
                 }
             )
         return out
+    def get_key_by_fingerprint(self, agent: str, fingerprint: str):
+        """Return a historical (or live) public key row for verify.
+
+        Prefers agent_keys history. Falls back to the live agents row when the
+        fingerprint still matches (covers DBs created before agent_keys).
+        Never returns private key material — pubkey only.
+        """
+        row = self._one(
+            "SELECT * FROM agent_keys WHERE agent = ? AND fingerprint = ?",
+            (agent, fingerprint),
+        )
+        if row is not None:
+            return row
+        live = self.get_agent(agent)
+        if live is not None and (live["fingerprint"] or "") == fingerprint:
+            return live
+        return None
+
     # -- checkpoints -------------------------------------------------------
+
     @staticmethod
     def _checkpoint_payload(at: int, label: str, head: str, events: int,
                             signer: str, fingerprint: str) -> bytes:
@@ -675,8 +788,19 @@ class Store:
 
         public = _keys.public_from_private(private)
         fingerprint = _keys.fingerprint(public)
-        if self.get_agent(signer) is None:
+        from . import identity as _identity
+
+        agent_row = self.get_agent(signer)
+        if agent_row is None:
             raise ValueError(f"{signer} is not enrolled, so cannot sign a checkpoint")
+        if _identity.is_revoked(agent_row):
+            raise ValueError(f"{signer} is revoked, so cannot sign a checkpoint")
+        enrolled_fp = agent_row["fingerprint"] or ""
+        if not enrolled_fp or fingerprint != enrolled_fp:
+            raise ValueError(
+                f"private key fingerprint does not match enrolled key for {signer}; "
+                "refusing to sign a checkpoint with a stranger key"
+            )
         with self._write_lock:
             last = self.conn.execute(
                 "SELECT id, hash FROM events ORDER BY id DESC LIMIT 1"
@@ -740,17 +864,20 @@ class Store:
         if not notices or notices[-1].get("head") != tip.get("head"):
             notices = list(notices) + [tip]
         results = []
+        warnings = []
         for notice in notices:
-            agent_row = self.get_agent(notice["signer"])
+            if self.get_agent(notice["signer"]) is None:
-            if agent_row is None:
                 results.append({"ok": False, "head": notice.get("head"),
                                 "reason": f"signer {notice['signer']} no longer enrolled"})
                 continue
-            if agent_row["fingerprint"] != notice.get("fingerprint"):
+            key_row = self.get_key_by_fingerprint(
+                notice["signer"], notice.get("fingerprint") or ""
+            )
+            if key_row is None:
                 results.append({"ok": False, "head": notice.get("head"),
-                                "reason": "signer key changed since the tip was published"})
+                                "reason": "signer key for this fingerprint is unknown"})
                 continue
-            public = _keys.from_public_bytes(agent_row["pubkey"])
+            public = _keys.from_public_bytes(key_row["pubkey"])
             checked = _anchor.verify_notice(notice, public)
             if not checked["ok"]:
                 results.append({"ok": False, "head": notice.get("head"),
@@ -770,11 +897,17 @@ class Store:
                               "(database rewrite cannot erase the off-box tip)",
                 })
                 continue
-            results.append({"ok": True, "head": notice["head"],
+            entry = {"ok": True, "head": notice["head"],
-                            "events": notice["events"], "signer": notice["signer"]})
+                     "events": notice["events"], "signer": notice["signer"]}
+            retired_at = key_row["retired_at"] if "retired_at" in key_row.keys() else None
+            if retired_at is not None and notice.get("at", 0) > retired_at:
+                entry["flagged"] = True
+                entry["reason"] = "notice timestamp is after the signing key was retired"
+                warnings.append(entry)
+            results.append(entry)
         bad = [r for r in results if not r["ok"]]
         return {"ok": not bad, "anchors": len(results), "failures": bad,
-                "tip": tip, "path": self.anchor_path}
+                "warnings": warnings, "tip": tip, "path": self.anchor_path}
 
     def checkpoints(self) -> List[Dict[str, Any]]:
         rows = self.conn.execute("SELECT * FROM checkpoints ORDER BY id ASC").fetchall()
@@ -790,22 +923,23 @@ class Store:
         from . import keys as _keys
 
         results = []
+        warnings = []
         for row in self.conn.execute("SELECT * FROM checkpoints ORDER BY id ASC"):
-            agent_row = self.get_agent(row["signer"])
+            if self.get_agent(row["signer"]) is None:
-            if agent_row is None:
                 results.append({"id": row["id"], "ok": False,
                                 "reason": f"signer {row['signer']} no longer enrolled"})
                 continue
-            if agent_row["fingerprint"] != row["fingerprint"]:
+            key_row = self.get_key_by_fingerprint(row["signer"], row["fingerprint"])
+            if key_row is None:
                 results.append({"id": row["id"], "ok": False,
-                                "reason": "signer key changed since the checkpoint was made"})
+                                "reason": "signer key for this fingerprint is unknown"})
                 continue
             payload = self._checkpoint_payload(
                 row["at"], row["label"], row["head"], row["events"],
                 row["signer"], row["fingerprint"],
             )
             try:
-                public = _keys.from_public_bytes(agent_row["pubkey"])
+                public = _keys.from_public_bytes(key_row["pubkey"])
                 # verify() returns None on success and raises on failure, so it
                 # must be called, not inspected.
                 public.verify(base64.b64decode(row["signature"]), payload)
@@ -823,9 +957,16 @@ class Store:
                 results.append({"id": row["id"], "ok": False,
                                 "reason": "chain head at that position no longer matches"})
                 continue
-            results.append({"id": row["id"], "ok": True})
+            entry = {"id": row["id"], "ok": True}
+            retired_at = key_row["retired_at"] if "retired_at" in key_row.keys() else None
+            if retired_at is not None and row["at"] > retired_at:
+                entry["flagged"] = True
+                entry["reason"] = "checkpoint timestamp is after the signing key was retired"
+                warnings.append(entry)
+            results.append(entry)
         bad = [r for r in results if not r["ok"]]
-        return {"ok": not bad, "checkpoints": len(results), "failures": bad}
+        return {"ok": not bad, "checkpoints": len(results),
+                "failures": bad, "warnings": warnings}
 
     # -- housekeeping ------------------------------------------------------
     def sweep(self) -> Dict[str, int]:

sigil/viewcodes.py

@@ -91,9 +91,18 @@ def issue_code(
     if not store.allow(f"code_issue:{agent}", limit=limit, window=window):
         raise errors.RateLimited(f"too many view codes for {agent}")
 
+    from . import identity as _identity
+
     agent_row = store.get_agent(agent)
     if agent_row is None:
         raise errors.UnknownAgent(f"{agent} is not enrolled")
+    # Re-check after resolve: revoke/rekey can land between resolve and put_code.
+    if _identity.is_revoked(agent_row) or not _identity.has_live_key(agent_row):
+        raise errors.UnknownAgent(f"{agent} is revoked or has no live key")
+    live_fp = agent_row["fingerprint"] or ""
+    sess_fp = principal.get("fingerprint") or ""
+    if not live_fp or sess_fp != live_fp:
+        raise errors.SessionExpired("session key epoch no longer current")
 
     granted = list(scopes if scopes is not None else sessions.HUMAN_VIEW_SCOPES)
     # Refuse to bake write or act scopes into a human code at issue time.
@@ -115,12 +124,13 @@ def issue_code(
         granted,
         redeem_expires_at=now + code_ttl,
         view_ttl=view_ttl,
+        fingerprint=live_fp,
     )
     store.record(
         "view_code.issued",
         actor=agent,
         subject=f"{agent}'s human",
-        fingerprint=agent_row["fingerprint"],
+        fingerprint=live_fp,
         detail={
             "code_ref": _code_ref(code),
             "scopes": granted,
@@ -134,7 +144,6 @@ def issue_code(
         "code_ttl": code_ttl,
         "view_ttl": view_ttl,
         "redeem_expires_at": now + code_ttl,
-        "view_ttl": view_ttl,
     }
 
 
@@ -155,19 +164,25 @@ def redeem_code(store: Store, code: str) -> dict:
 
     agent = row["agent"]
 
-    # Defense in depth: revoke/rekey already invalidate unused codes, but refuse
+    # Defense in depth: refuse if agent revoked, wiped, or rekeyed since issue.
-    # here too if the agent is currently revoked or missing so a missed
-    # invalidation cannot mint a human_via_agent session.
     from . import identity as _identity
     agent_row = store.get_agent(agent)
-    if agent_row is None or _identity.is_revoked(agent_row):
+    code_fp = row["fingerprint"] if "fingerprint" in row.keys() else None
+    live_fp = (agent_row["fingerprint"] or "") if agent_row is not None else ""
+    bad = (
+        agent_row is None
+        or _identity.is_revoked(agent_row)
+        or not _identity.has_live_key(agent_row)
+        or (code_fp is not None and code_fp != live_fp)
+    )
+    if bad:
         if not store.allow(f"code_redeem_fail:{agent}"):
             raise errors.RateLimited("too many redemption attempts")
         store.record(
             "view_code.redeem_refused",
             actor=agent,
             subject=f"{agent}'s human",
-            detail={"reason": "agent revoked or unknown"},
+            detail={"reason": "agent revoked, wiped, or rekeyed"},
         )
         raise errors.CodeInvalid("that code is not redeemable")
 
@@ -216,6 +231,7 @@ def redeem_code(store: Store, code: str) -> dict:
         _json.loads(row["scopes"]),
         row["view_ttl"],
         sessions._ISSUER,
+        fingerprint=live_fp,
     )
     return sessions.issue_view_session(store, grant)
 

tests/test_hardening.py

@@ -360,3 +360,215 @@ class TestAgentIdValidation(unittest.TestCase):
 
 if __name__ == "__main__":
     unittest.main()
+
+
+class TestClaimCodeExpiryCAS(unittest.TestCase):
+    """R6: claim_code CAS must include redeem_expires_at predicate."""
+
+    def test_claim_code_after_expiry_returns_false(self):
+        store, private = helpers.fresh()
+        issued = helpers.issue(store, private, code_ttl=1, view_ttl=60)
+        digest = viewcodes._hash_code(issued["code"])
+        # Force expiry in the row.
+        store.conn.execute(
+            "UPDATE codes SET redeem_expires_at = ? WHERE code_hash = ?",
+            (int(time.time()) - 1, digest),
+        )
+        store.conn.commit()
+        self.assertFalse(store.claim_code(digest))
+        row = store.get_code(digest)
+        self.assertIsNone(row["used_at"])
+
+
+class TestEnrolRekeyRateLimit(unittest.TestCase):
+    """N3: enrol_rekey uses a dedicated rekey: bucket; junk cannot lock ops."""
+
+    def test_exhausting_enrol_bucket_does_not_block_rekey(self):
+        store, _ = helpers.fresh("limited")
+        for _ in range(20):
+            store.allow("enrol:limited")
+        secret = identity.seed_bootstrap(store, "limited")
+        # Valid rekey must succeed even if enrol: is exhausted.
+        identity.enrol_rekey(
+            store, "limited", keys.export_public_b64(keys.generate()[1]), secret
+        )
+
+    def test_junk_rekey_fills_rekey_bucket_not_enrol(self):
+        store, _ = helpers.fresh("victim")
+        for _ in range(15):
+            try:
+                identity.enrol_rekey(
+                    store, "victim", keys.export_public_b64(keys.generate()[1]), "junk"
+                )
+            except (errors.EnrolmentFailed, errors.RateLimited):
+                pass
+        # enrol: bucket still usable
+        self.assertTrue(store.allow("enrol:victim"))
+        # Valid ops rekey still works: failures charge rekey: only after bad secret,
+        # and a valid secret bypasses the limiter.
+        secret = identity.seed_bootstrap(store, "victim")
+        identity.enrol_rekey(
+            store, "victim", keys.export_public_b64(keys.generate()[1]), secret
+        )
+
+    def test_failed_rekey_eventually_rate_limited(self):
+        store, _ = helpers.fresh("hammer")
+        hit = False
+        for _ in range(30):
+            try:
+                identity.enrol_rekey(
+                    store, "hammer", keys.export_public_b64(keys.generate()[1]), "nope"
+                )
+            except errors.RateLimited:
+                hit = True
+                break
+            except errors.EnrolmentFailed:
+                pass
+        self.assertTrue(hit, "junk rekey attempts should eventually RateLimited")
+
+
+
+class TestBootstrapRowDeletedOnSpend(unittest.TestCase):
+    """R8: spent bootstrap secrets are deleted, not retained as hashes."""
+
+    def test_spend_deletes_the_row(self):
+        store = Store(":memory:")
+        secret = identity.seed_bootstrap(store, "dave")
+        digest = __import__("hashlib").sha256(secret.encode()).hexdigest()
+        self.assertIsNotNone(store.conn.execute(
+            "SELECT 1 FROM bootstrap WHERE secret_hash = ?", (digest,)
+        ).fetchone())
+        owner = store.spend_bootstrap(digest)
+        self.assertEqual(owner, "dave")
+        self.assertIsNone(store.conn.execute(
+            "SELECT 1 FROM bootstrap WHERE secret_hash = ?", (digest,)
+        ).fetchone())
+
+
+class TestResolveRechecksAgentState(unittest.TestCase):
+    """N1: resolve must refuse sessions that outran revoke/rekey."""
+
+    def _plant_agent_session(self, store, agent, fingerprint):
+        """Insert a live session as if put_session won a race against revoke."""
+        import time as _t
+        token = "race-survivor-token"
+        store.put_session(
+            sessions.hash_token(token),
+            sessions.AGENT,
+            agent,
+            agent,
+            list(sessions.AGENT_SCOPES),
+            int(_t.time()) + 900,
+            fingerprint=fingerprint,
+        )
+        return token
+
+    def test_resolve_refuses_race_survivor_after_permanent_revoke(self):
+        store, private = helpers.fresh()
+        fp = store.get_agent("bigpickle")["fingerprint"]
+        identity.revoke(store, "bigpickle", reason="compromise")
+        # Session inserted *after* revoke (race); not marked revoked_at.
+        token = self._plant_agent_session(store, "bigpickle", fp)
+        with self.assertRaises(errors.SessionExpired):
+            sessions.resolve(store, token)
+
+    def test_resolve_refuses_stale_fingerprint_after_rekey(self):
+        store, private = helpers.fresh()
+        old_fp = store.get_agent("bigpickle")["fingerprint"]
+        new_pub = keys.generate()[1]
+        secret = identity.seed_bootstrap(store, "bigpickle")
+        identity.enrol_rekey(
+            store, "bigpickle", keys.export_public_b64(new_pub), secret
+        )
+        token = self._plant_agent_session(store, "bigpickle", old_fp)
+        with self.assertRaises(errors.SessionExpired):
+            sessions.resolve(store, token)
+
+    def test_redeem_refuses_code_after_rekey_even_if_not_invalidated(self):
+        """Fingerprint binding: plant a code with a stale fingerprint."""
+        store, private = helpers.fresh()
+        agent_row = store.get_agent("bigpickle")
+        old_fp = agent_row["fingerprint"]
+        # Issue normally, then surgically restore used_at and keep old fp after rekey
+        issued = helpers.issue(store, private)
+        digest = viewcodes._hash_code(issued["code"])
+        new_pub = keys.generate()[1]
+        secret = identity.seed_bootstrap(store, "bigpickle")
+        identity.enrol_rekey(
+            store, "bigpickle", keys.export_public_b64(new_pub), secret
+        )
+        # Rekey invalidated the code; un-burn it to simulate put_code after invalidate.
+        store.conn.execute(
+            "UPDATE codes SET used_at = NULL, fingerprint = ? WHERE code_hash = ?",
+            (old_fp, digest),
+        )
+        store.conn.commit()
+        with self.assertRaises(errors.CodeInvalid):
+            viewcodes.redeem_code(store, issued["code"])
+
+    def test_redeem_refuses_without_live_key(self):
+        store, private = helpers.fresh()
+        issued = helpers.issue(store, private)
+        digest = viewcodes._hash_code(issued["code"])
+        identity.revoke(store, "bigpickle", reason="compromise")
+        identity.reinstate(store, "bigpickle")  # ban lifted, key still wiped
+        store.conn.execute(
+            "UPDATE codes SET used_at = NULL WHERE code_hash = ?", (digest,)
+        )
+        store.conn.commit()
+        with self.assertRaises(errors.CodeInvalid):
+            viewcodes.redeem_code(store, issued["code"])
+
+    def test_verify_then_revoke_session_unusable(self):
+        """Session minted just before revoke must not resolve."""
+        store, private = helpers.fresh()
+        chal = identity.challenge(store, "bigpickle")
+        sig = helpers.sign(private, chal["nonce"])
+        sess = identity.verify(store, chal["nonce"], sig)
+        identity.revoke(store, "bigpickle", reason="compromise")
+        with self.assertRaises(errors.SessionExpired):
+            sessions.resolve(store, sess["token"])
+
+
+class TestHumanSessionFingerprintEpoch(unittest.TestCase):
+    """N7: rekey must kill race-surviving human_via_agent sessions too."""
+
+    def test_resolve_refuses_stale_human_fingerprint_after_rekey(self):
+        store, private = helpers.fresh()
+        old_fp = store.get_agent("bigpickle")["fingerprint"]
+        # Plant a human session as if redeem's put_session won a race against rekey.
+        import time as _t
+        token = "human-race-survivor"
+        store.put_session(
+            sessions.hash_token(token),
+            sessions.HUMAN_VIA_AGENT,
+            "bigpickle's human",
+            "bigpickle",
+            list(sessions.HUMAN_VIEW_SCOPES),
+            int(_t.time()) + 3600,
+            granted_by="bigpickle",
+            fingerprint=old_fp,
+        )
+        new_pub = keys.generate()[1]
+        secret = identity.seed_bootstrap(store, "bigpickle")
+        identity.enrol_rekey(
+            store, "bigpickle", keys.export_public_b64(new_pub), secret
+        )
+        # Clear revoked_at that rekey set, to isolate the fingerprint check.
+        store.conn.execute(
+            "UPDATE sessions SET revoked_at = NULL, revoked_reason = NULL"
+            " WHERE token_hash = ?",
+            (sessions.hash_token(token),),
+        )
+        store.conn.commit()
+        with self.assertRaises(errors.SessionExpired) as ctx:
+            sessions.resolve(store, token)
+        self.assertIn("key epoch", str(ctx.exception))
+
+    def test_issue_code_return_has_single_view_ttl(self):
+        """N8: issue_code return dict must not duplicate view_ttl."""
+        import inspect
+        from sigil import viewcodes as vc
+        src = inspect.getsource(vc.issue_code)
+        # Count literal "view_ttl" keys in the return dict construction region.
+        self.assertEqual(src.count('"view_ttl":'), 1, src[src.rfind("return"):])

tests/test_production.py

@@ -133,15 +133,25 @@ class TestSignedCheckpoints(unittest.TestCase):
         with self.assertRaises(ValueError):
             stranger.checkpoint(self.private, "not-enrolled")
 
-    def test_checkpoint_after_rekey_is_flagged(self):
+    def test_checkpoint_refuses_enrolled_name_with_wrong_key(self):
+        # R4: signer name is enrolled, but private key is not the enrolled one.
+        before = len(self.store.checkpoints())
+        other_private, _ = keys.generate()
+        with self.assertRaises(ValueError) as ctx:
+            self.store.checkpoint(other_private, "bigpickle")
+        self.assertIn("does not match enrolled key", str(ctx.exception))
+        self.assertEqual(len(self.store.checkpoints()), before)
+
+    def test_checkpoint_after_rekey_still_verifies_via_history(self):
+        # N2: historical checkpoints verify against retired public keys.
         secret = identity.seed_bootstrap(self.store, "bigpickle")
         identity.enrol_rekey(
             self.store, "bigpickle",
             keys.export_public_b64(keys.generate()[1]), secret,
         )
         result = self.store.verify_checkpoints()
-        self.assertFalse(result["ok"])
+        self.assertTrue(result["ok"], result)
-        self.assertIn("key changed", result["failures"][0]["reason"])
+        self.assertEqual(result["failures"], [])
 
     def test_empty_log_checkpoints_cleanly(self):
         store, private = helpers.fresh()
@@ -482,3 +492,75 @@ class TestRedeemRateLimitIsolation(unittest.TestCase):
             self.fail("successes must not share the fail bucket")
         except errors.SigilError:
             pass
+
+
+class TestKeyHistoryKeepsCheckpointsVerifiable(unittest.TestCase):
+    """N2: permanent revoke / rekey must not make honest checkpoints unverifiable."""
+
+    def test_checkpoints_verify_after_signer_permanent_revoke(self):
+        import tempfile, os
+        d = tempfile.mkdtemp()
+        anchor = os.path.join(d, "tip")
+        store = Store(":memory:", anchor_path=anchor)
+        private, _ = helpers.enrol(store, "signer")
+        store.record("identity.enrolled", actor="signer", subject="signer")
+        store.checkpoint(private, "signer", "pre-compromise")
+        before = store.verify_checkpoints()
+        self.assertTrue(before["ok"], before)
+        anchors_before = store.verify_external_anchors()
+        self.assertTrue(anchors_before["ok"], anchors_before)
+        identity.revoke(store, "signer", reason="compromise")
+        after = store.verify_checkpoints()
+        self.assertTrue(after["ok"], after)
+        self.assertEqual(after["failures"], [])
+        anchors_after = store.verify_external_anchors()
+        self.assertTrue(anchors_after["ok"], anchors_after)
+        # Live key wiped; history retained.
+        self.assertFalse(identity.has_live_key(store.get_agent("signer")))
+        hist = store.conn.execute(
+            "SELECT fingerprint, retired_at FROM agent_keys WHERE agent = ?",
+            ("signer",),
+        ).fetchall()
+        self.assertEqual(len(hist), 1)
+        self.assertIsNotNone(hist[0]["retired_at"])
+
+    def test_private_key_never_in_agent_keys(self):
+        store, private = helpers.fresh("carol")
+        cols = [r["name"] for r in store.conn.execute("PRAGMA table_info(agent_keys)")]
+        self.assertNotIn("private", cols)
+        self.assertNotIn("privkey", cols)
+        row = store.conn.execute("SELECT * FROM agent_keys WHERE agent = ?", ("carol",)).fetchone()
+        self.assertEqual(len(row["pubkey"]), 32)
+
+
+class TestEnrolAfterPermanentRevoke(unittest.TestCase):
+    """N4: enrol must not burn the seed when the agent row still exists."""
+
+    def test_enrol_after_permanent_revoke_does_not_burn_seed(self):
+        store, private = helpers.fresh()
+        identity.revoke(store, "bigpickle", reason="compromise")
+        identity.reinstate(store, "bigpickle")
+        secret = identity.seed_bootstrap(store, "bigpickle")
+        with self.assertRaises(errors.EnrolmentFailed) as ctx:
+            identity.enrol(
+                store, "bigpickle", keys.export_public_b64(keys.generate()[1]), secret
+            )
+        self.assertIn("enrol_rekey", str(ctx.exception))
+        # Seed still usable for the correct path.
+        identity.enrol_rekey(
+            store, "bigpickle", keys.export_public_b64(keys.generate()[1]), secret
+        )
+
+
+class TestSuspendedSignerCannotCheckpoint(unittest.TestCase):
+    """N5: timed-suspended signer must not checkpoint."""
+
+    def test_timed_suspend_refuses_checkpoint(self):
+        import time
+        store, private = helpers.fresh()
+        identity.revoke(
+            store, "bigpickle", until=int(time.time()) + 3600, reason="pause"
+        )
+        with self.assertRaises(ValueError) as ctx:
+            store.checkpoint(private, "bigpickle")
+        self.assertIn("revoked", str(ctx.exception).lower())

tests/test_sealed.py

@@ -124,3 +124,30 @@ class TestSealedStore(unittest.TestCase):
 
 if __name__ == "__main__":
     unittest.main()
+
+
+class TestPlaintextWorkingCopyHardening(unittest.TestCase):
+    """R5: plaintext tmp must be 0600; SQLCipher remains deferred."""
+
+    def test_plaintext_working_copy_is_owner_only(self):
+        import tempfile
+        from sigil.sealed import SealedStore
+        from sigil import identity, keys
+
+        d = tempfile.mkdtemp()
+        path = os.path.join(d, "sealed.db")
+        store = SealedStore(path, "test-passphrase-ok")
+        try:
+            mode = os.stat(store._plain_path).st_mode & 0o777
+            self.assertEqual(mode, 0o600, oct(mode))
+            dir_mode = os.stat(store._tmpdir.name).st_mode & 0o777
+            self.assertEqual(dir_mode, 0o700, oct(dir_mode))
+            secret = identity.seed_bootstrap(store, "alice")
+            _, pub = keys.generate()
+            identity.enrol(store, "alice", keys.export_public_b64(pub), secret)
+            store.flush()
+            # export.db must not linger world-readable after flush
+            export = os.path.join(store._tmpdir.name, "export.db")
+            self.assertFalse(os.path.exists(export))
+        finally:
+            store.close()