AI Answer Ledger: the hash chain

The ledger records each AI call the day it is asked and shows it only once its 30-day window has closed and it has been scored. That leaves a question the scoreboard cannot answer by itself: was any call changed after the price moved? Each ask day’s calls are sealed into a SHA-256 digest when they are stored, and the digest is published here while the calls stay hidden. Every digest includes the one before it, so changing any stored call would change its own day’s digest and every digest after it.

Check it yourself

1. Keep a copy of the chain today, before the newest calls are scored: curl -s https://stocktools.ai/api/ai-answer-ledger/chain > chain-saved.json. A public web archive snapshot of this page works as well.
2. After a day’s calls are scored and shown on the ledger page, its link carries the salt and the calls exactly as they were sealed. Run the script below with Node 18 or later and your saved copy: node verify-ledger-chain.mjs chain-saved.json.
3. Every revealed link should print rows hash to the digest, every link linked, and every link you kept same as your copy. Then check that the calls in the JSON are the ones the ledger page shows for that day.

// verify-ledger-chain.mjs   run: node verify-ledger-chain.mjs [your-saved-copy.json]
import { createHash } from 'node:crypto';
import { readFileSync } from 'node:fs';

const chain = await (await fetch('https://stocktools.ai/api/ai-answer-ledger/chain')).json();
const saved = process.argv[2] ? JSON.parse(readFileSync(process.argv[2], 'utf8')) : { links: [] };
const before = new Map(saved.links.map((l) => [l.seq, l.digest]));
let prev = chain.genesis;
for (const l of chain.links) {
  const linked = l.prevDigest === prev ? 'linked' : 'BROKEN LINK';
  let rows = 'hidden until scored';
  if (l.salt) {
    const d = createHash('sha256').update(`${l.prevDigest}\n${l.salt}\n${JSON.stringify(l.rows)}`).digest('hex');
    rows = d === l.digest ? 'rows hash to the digest' : 'ROWS DO NOT MATCH';
  }
  const kept = !before.has(l.seq) ? 'not in your copy' : before.get(l.seq) === l.digest ? 'same as your copy' : 'CHANGED since your copy';
  console.log(l.seq, l.day, linked, rows, kept);
  prev = l.digest;
}

What is hashed

For each link: sha256(previous digest + "\n" + salt + "\n" + rows), written as lowercase hex. The rows are that day’s calls sorted by id, each with these fields in this order, as JSON with no spaces: id, ticker, model, promptVersion, askedOn, dueOn, call, reason, priceAtAsk, askSession. In Python, json.dumps(rows, separators=(',', ':'), ensure_ascii=False) gives the same text from the JSON’s rows. The first link’s previous digest is 64 zeros. These are the fields recorded when a call is asked. The fields written at scoring time (the closing price on the due date, the move and the result) are left out, because they come from the outcome and cannot be sealed before it.

Why a salt: every field except the call is guessable (ten known tickers, the model, the dates), and a day has at most 3¹⁰, about 59,000, combinations of calls. Without a secret ingredient, anyone could hash every combination and read the hidden calls off the published digest. Each link mixes in 32 random bytes that stay private until its calls are shown, and are published beside them then.

What this does not prove: that a call was never skipped. A day can hold fewer than ten calls when a quote or an answer could not be read, and the count of each link is published so a short day is visible. The chain is stored by us, so its protection comes from copies other people keep; the check above is only as strong as the oldest copy you compare against.

Keep going: the AI Answer Ledger · the settlement referee · methodology