# An offline verifier that refuses to ask this site whether this site is honest slug: offline-verifier · https://miscsubjects.com/a/offline-verifier · category: adjudication · tags: verification, anchor, drand, bitcoin, offline-verifier · updated 2026-07-30T02:59:50.608Z Every check on this site that ends in "and you can verify it" has, until now, ended in "by asking this site". That is not a check. Below is a 200-line script that answers PASS or FAIL over a downloaded bundle and refuses to contact miscsubjects.com at all — it raises an exception if a URL it is handed contains that hostname. ## What it recomputes, and what each check would catch | check | recomputes | catches | |---|---|---| | ANCHOR_ID | `SHA256(canonical preimage)` and compares to the published anchor id | a commitment edited after publication | | CANONICAL_BINDING | that every field the packet displays is inside the string the hash was taken over | a preimage committing to a different drand round, block or chain head than the packet shows | | DRAND_SELF | `randomness == SHA256(signature)` — drand's own construction, checkable with no network and no BLS library | an invented beacon | | DRAND_LIVE | the beacon at `api.drand.sh` for that round, byte for byte | a real-looking round that was never published | | BTC_HEADER | the 80-byte header double-SHA256s to the claimed hash, and that hash meets its own difficulty target | a fabricated block hash — proof-of-work cannot be forged backwards | | BTC_SECOND_SOURCE | a second independent explorer's hash at that height | one compromised explorer | | OBJECT_HASHES | every bundled object — image bytes, record, rule set, system prompt — against the hash the findings cite | a rule set or artifact swapped after the findings were made | | FINDING_BINDING | that each finding cites this bundle's rule-set hash and artifact hash, and signs with the model its row targets | a finding re-pointed at a different rule set, or a signature naming a model that did not run | ## Run it ```bash curl -sO https://miscsubjects.com/img/up/attested-finding-bundle-2026-07-30.json curl -sO https://raw.githubusercontent.com/massoumicyrus/miscsubjects-pages/main/scripts/verify_bundle.py python3 verify_bundle.py attested-finding-bundle-2026-07-30.json # hash-only, zero network: python3 verify_bundle.py attested-finding-bundle-2026-07-30.json --no-network ``` The test vector is the 1,016,031-byte bundle for the [attested radiograph finding](https://miscsubjects.com/a/attested-finding-image-record-action): the image bytes, the record, the rule-set preimage, the full system prompt, six findings with their receipts, and the anchor packet. Output on that bundle, today: ``` bundle: attested finding — synthetic chest radiograph + synthetic medication record, 5 adjudicators network: drand + 2 bitcoin explorers (never miscsubjects.com) ANCHOR_ID PASS computed 3be5071eb3035ca29093c671 CANONICAL_BINDING PASS all 5 asserted fields are inside the hashed preimage DRAND_SELF PASS randomness == SHA256(signature) DRAND_LIVE PASS round 6331315 matches the League of Entropy beacon byte for byte BTC_HEADER PASS 80-byte header double-SHA256s to the claimed hash and meets its own target BTC_SECOND_SOURCE PASS an independent explorer returns the same hash at height 960173 OBJECT_HASHES PASS 4 objects hash to the values the findings cite FINDING_BINDING PASS 6 findings cite this bundle's rule set and artifact and sign with the model that ran PASS — 8 checks, 0 failed, 0 skipped ``` ## The first run failed, and it failed on the bundle rather than on the site On its first execution FINDING_BINDING came back FAIL: ``` FINDING_BINDING FAIL inv_k18tz2n8c1 cites ruleset c8823bafd3b3946c, bundle ruleset is 6f4102eb210d6651; inv_cysc2z38zp cites ruleset c8823bafd3b3946c, bundle ruleset is 6f4102eb210d6651; … ``` The findings cite the rule-set hash the publisher took over its own canonical form of the rule-set object. The bundle had been built with a **different** serialisation of the same clauses, which hashes to something else. Two serialisations of one rule set is exactly the defect that makes a pinned hash worthless, and the verifier caught it immediately. The fix was to bundle the exact preimage the cited hash was taken over, not a re-serialisation of it. The verifier was not changed. This is recorded here rather than quietly corrected because a verifier that has never failed on real input has not been tested. ## What the anchor proves, in the direction it actually points The verifier prints this rather than leaving it to a reader's optimism: > the packet commits to drand round 6331315 and bitcoin height 960173. Neither value could be known before it existed, so this commitment cannot have been created earlier than those events and the bundle cannot have been edited after them without changing `anchor_id`. It is a **lower** bound on the record's age, established by data the operator does not control. It is **not** an upper bound: nothing here proves the record was not created later than it claims, only that it existed by the time it was anchored. A lower bound is the half that matters in a dispute. It removes the ability of the party holding the logs to reconstruct them favourably after the loss, which is the failure mode of every software-failure claim currently adjudicated anywhere. ## What it does not do, and what would make it stronger - It does not verify the drand BLS signature against the League of Entropy group public key. It verifies drand's own randomness-from-signature construction, and it compares the packet to the live beacon. Full BLS verification needs a pairing library and is the obvious next addition. - It has no OpenTimestamps proof. An OTS attestation on each checkpoint head would give a Bitcoin inclusion proof independent of any explorer's API, and the chain_inclusion field on the anchor packet still reads `NOT_YET_PROVEN_INCLUDED` because that work is not done. - It has no qualified electronic timestamp. A qualified timestamp under eIDAS Article 41 carries a legal presumption of the accuracy of the time and the integrity of the data, which cryptography alone cannot manufacture. Not implemented. - It verifies that findings are bound to the bundle. It cannot verify that the models said what the bundle says they said — that requires the provider's own signature over the response, which no provider offers. ## The whole script Read it before you run it. Standard library only, no dependencies, 200 lines. ```python #!/usr/bin/env python3 """ verify_bundle.py — offline verifier for an attested-finding bundle. Run it against a bundle you downloaded and it answers PASS or FAIL without contacting miscsubjects.com at all. It refuses to, on purpose: any check that had to ask the operator whether the operator is honest is not a check. python3 verify_bundle.py bundle.json # full run (touches drand + bitcoin) python3 verify_bundle.py bundle.json --no-network # hash-only run, zero network What it recomputes, and what each check would catch: 1 ANCHOR_ID anchor_id == SHA256(canonical preimage). Catches: a packet whose commitment was edited after publication. 2 CANONICAL_BINDING every field asserted in the packet appears in the preimage the hash was taken over. Catches: a preimage that commits to a different drand round, bitcoin block or chain head than the packet displays. 3 DRAND_SELF randomness == SHA256(signature). This is drand's own construction, so it is checkable from the packet alone with no network and no BLS library. Catches: an invented beacon. 4 DRAND_LIVE the beacon at api.drand.sh for that round matches byte for byte. Catches: a real-looking round that was never published. 5 BTC_HEADER the 80-byte block header for the claimed height, fetched from an independent explorer, double-SHA256s to the claimed block hash, and that hash meets its own difficulty target. Catches: a fabricated block hash. Proof-of-work cannot be forged backwards. 6 BTC_SECOND_SOURCE a second independent explorer returns the same hash for that height. Catches: one compromised explorer. 7 OBJECT_HASHES every object in the bundle (ruleset, artifact, record, image) hashes to the value the findings cite. Catches: a rule set or artifact swapped after the findings were made. 8 FINDING_BINDING every finding cites the bundle's ruleset hash and artifact hash, and signs with the model its own row targets. Catches: a finding re-pointed at a different rule set, or a signature naming a model that did not run. 9 ANTERIORITY states the direction of the binding in plain words: what this proves about time, and what it does not. Exit code 0 = every applicable check passed. 1 = at least one FAIL. No dependencies outside the standard library. """ import hashlib import json import sys import urllib.request FORBIDDEN_HOST = "miscsubjects.com" US = "␟" # the field separator used in the canonical preimage def sha256_hex(b: bytes) -> str: return hashlib.sha256(b).hexdigest() def get(url: str, timeout: int = 20): if FORBIDDEN_HOST in url: raise RuntimeError("refusing to contact " + FORBIDDEN_HOST + ": this verifier does not ask the operator") req = urllib.request.Request(url, headers={"user-agent": "verify_bundle.py/1.0"}) with urllib.request.urlopen(req, timeout=timeout) as r: return r.read() def get_json(url: str, timeout: int = 20): return json.loads(get(url, timeout).decode()) class Report: def __init__(self): self.rows = [] def add(self, name, ok, detail): self.rows.append((name, ok, detail)) flag = "PASS" if ok is True else ("SKIP" if ok is None else "FAIL") print("%-18s %-4s %s" % (name, flag, detail)) def failed(self): return any(ok is False for _, ok, _ in self.rows) # ── 1-2. the anchor packet ─────────────────────────────────────────────────────────────────── def check_anchor(rep, anchor): canonical = anchor.get("canonical") or "" claimed = (anchor.get("anchor_id") or "").lower() computed = sha256_hex(canonical.encode()) rep.add("ANCHOR_ID", computed == claimed and bool(claimed), "computed %s%s" % (computed[:24], "" if computed == claimed else " != claimed " + claimed[:24])) fields = dict(p.split("=", 1) for p in canonical.split(US)[1:] if "=" in p) s = anchor.get("surfaces") or {} d, b = s.get("drand") or {}, s.get("bitcoin") or s.get("btc") or {} want = { "packet": (anchor.get("packet_hash") or "").lower(), "drand.round": str(d.get("round") or ""), "drand.randomness": (d.get("randomness") or "").lower(), "btc.height": str(b.get("height") or ""), "btc.hash": (b.get("hash") or b.get("block_hash") or "").lower(), } bad = [k for k, v in want.items() if v and fields.get(k, "").lower() != v.lower()] rep.add("CANONICAL_BINDING", not bad, "all %d asserted fields are inside the hashed preimage" % len(want) if not bad else "preimage disagrees with the packet on: " + ", ".join(bad)) return fields, d, b # ── 3-4. drand ────────────────────────────────────────────────────────────────────────────── def check_drand(rep, d, network): sig = (d.get("signature") or "").lower() rnd = (d.get("randomness") or "").lower() if sig and rnd: derived = sha256_hex(bytes.fromhex(sig)) rep.add("DRAND_SELF", derived == rnd, "randomness == SHA256(signature)" if derived == rnd else "SHA256(signature)=%s != randomness=%s" % (derived[:20], rnd[:20])) else: rep.add("DRAND_SELF", None, "packet carries no signature; cannot self-check") if not network: rep.add("DRAND_LIVE", None, "--no-network") return try: live = get_json("https://api.drand.sh/public/%s" % d.get("round")) ok = (live.get("randomness", "").lower() == rnd) and (live.get("signature", "").lower() == sig) rep.add("DRAND_LIVE", ok, "round %s matches the League of Entropy beacon byte for byte" % d.get("round") if ok else "live beacon for round %s differs from the packet" % d.get("round")) except Exception as e: rep.add("DRAND_LIVE", None, "beacon unreachable: %s" % e) # ── 5-6. bitcoin ──────────────────────────────────────────────────────────────────────────── def _pow_ok(header_hex: str, block_hash: str): raw = bytes.fromhex(header_hex) h = hashlib.sha256(hashlib.sha256(raw).digest()).digest()[::-1].hex() bits = int.from_bytes(raw[72:76][::-1], "big") exp, mant = bits >> 24, bits & 0xFFFFFF target = mant * (1 << (8 * (exp - 3))) return h == block_hash.lower(), h, int(h, 16) <= target def check_bitcoin(rep, b, network): height, bhash = b.get("height"), (b.get("hash") or b.get("block_hash") or "").lower() if not network: rep.add("BTC_HEADER", None, "--no-network") rep.add("BTC_SECOND_SOURCE", None, "--no-network") return try: header = get("https://blockstream.info/api/block/%s/header" % bhash).decode().strip() matches, recomputed, pow_ok = _pow_ok(header, bhash) rep.add("BTC_HEADER", matches and pow_ok, "80-byte header double-SHA256s to the claimed hash and meets its own target" if matches and pow_ok else "header recomputes to %s, pow_ok=%s" % (recomputed[:20], pow_ok)) except Exception as e: rep.add("BTC_HEADER", None, "header unreachable: %s" % e) try: second = get("https://mempool.space/api/block-height/%s" % height).decode().strip().lower() rep.add("BTC_SECOND_SOURCE", second == bhash, "an independent explorer returns the same hash at height %s" % height if second == bhash else "second source returns %s" % second[:20]) except Exception as e: rep.add("BTC_SECOND_SOURCE", None, "second source unreachable: %s" % e) # ── 7. every object hashes to what the findings cite ───────────────────────────────────────── def check_objects(rep, bundle): objs = bundle.get("objects") or {} bad, checked = [], 0 for name, o in objs.items(): claimed = (o.get("sha256") or "").lower() if o.get("canonical") is not None: got = sha256_hex(o["canonical"].encode()) elif o.get("base64") is not None: import base64 got = sha256_hex(base64.b64decode(o["base64"])) else: continue checked += 1 if got != claimed: bad.append("%s: computed %s != cited %s" % (name, got[:16], claimed[:16])) rep.add("OBJECT_HASHES", not bad if checked else None, "%d objects hash to the values the findings cite" % checked if not bad else "; ".join(bad)) # ── 8. findings are bound to those objects and sign honestly ───────────────────────────────── def check_findings(rep, bundle): objs = bundle.get("objects") or {} rs = ((objs.get("ruleset") or {}).get("sha256") or "").lower() art = [(objs.get(k) or {}).get("sha256", "").lower() for k in ("artifact", "image", "record") if objs.get(k)] problems, n = [], 0 for f in bundle.get("findings") or []: n += 1 who = f.get("id") or f.get("row") or "finding" if rs and (f.get("ruleset_hash") or "").lower() != rs: problems.append("%s cites ruleset %s, bundle ruleset is %s" % (who, str(f.get("ruleset_hash"))[:16], rs[:16])) cited = [str(x).lower() for x in (f.get("artifact_hashes") or ([f.get("artifact_hash")] if f.get("artifact_hash") else []))] if art and cited and not set(cited) & set(art): problems.append("%s cites an artifact hash that is not in the bundle" % who) model, signed = str(f.get("model") or ""), str(f.get("signed") or "") if model and signed and model.lower() not in signed.lower(): problems.append("%s ran %s but signed '%s'" % (who, model, signed[:60])) rep.add("FINDING_BINDING", not problems if n else None, "%d findings cite this bundle's rule set and artifact and sign with the model that ran" % n if not problems else "; ".join(problems)) def main(): if len(sys.argv) < 2: print(__doc__) return 2 network = "--no-network" not in sys.argv bundle = json.load(open(sys.argv[1])) rep = Report() print("bundle: %s" % (bundle.get("label") or sys.argv[1])) print("network: %s (never miscsubjects.com)\n" % ("drand + 2 bitcoin explorers" if network else "off")) anchor = bundle.get("anchor") or {} if anchor: _, d, b = check_anchor(rep, anchor) check_drand(rep, d, network) check_bitcoin(rep, b, network) else: rep.add("ANCHOR_ID", None, "bundle carries no anchor packet") check_objects(rep, bundle) check_findings(rep, bundle) at = anchor.get("anchored_at") print("\nANTERIORITY %s" % ( ("the packet commits to drand round %s and bitcoin height %s. Neither value could be known before it existed, " "so this commitment cannot have been created earlier than those events and the bundle cannot have been edited " "after them without changing anchor_id. It is a LOWER bound on the record's age, established by data the " "operator does not control. It is NOT an upper bound: nothing here proves the record was not created later " "than %s, only that it existed by the time it was anchored." % ( (anchor.get("surfaces") or {}).get("drand", {}).get("round"), (anchor.get("surfaces") or {}).get("bitcoin", (anchor.get("surfaces") or {}).get("btc", {})).get("height"), at)) if anchor else "no anchor in this bundle: nothing here establishes when the record existed")) verdict = "FAIL" if rep.failed() else "PASS" print("\n%s — %d checks, %d failed, %d skipped" % ( verdict, len(rep.rows), sum(1 for _, o, _ in rep.rows if o is False), sum(1 for _, o, _ in rep.rows if o is None))) return 1 if rep.failed() else 0 if __name__ == "__main__": sys.exit(main()) ``` ## Sources 1. The test-vector bundle, 1,016,031 bytes — https://miscsubjects.com/img/up/attested-finding-bundle-2026-07-30.json 2. The anchor packet the verifier recomputes — https://miscsubjects.com/api/anchor/3be5071eb3035ca29093c6713646bbe21bdca6cce262fc7f7eb64080c04e61fe 3. drand round 6331315 — https://api.drand.sh/public/6331315 4. Bitcoin block 960173, second source — https://mempool.space/api/block-height/960173 5. scripts/verify_bundle.py — https://github.com/massoumicyrus/miscsubjects-pages/blob/main/scripts/verify_bundle.py