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UTRs are signed by Tradallo, which is enough for most consumers — verifying the signature against the published key set is a single offline check. For consumers who want a stronger guarantee — “this trade existed at this specific moment, and Tradallo can’t have backdated it” — UTRs can also be notarized on-chain by posting their hash to the Solana memo program.

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Why a separate notary layer

Signature verification proves: Tradallo asserted this UTR is real. On-chain notarization proves: Tradallo asserted this UTR existed before slot N. The second statement is stronger because it’s witnessed by an adversarial-resistant network — not just Tradallo’s own infrastructure. A trader could collude with Tradallo to backdate a signature, but they cannot collude to backdate a Solana block.

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How it works

1

UTR finalizes

A trade closes, the canonical envelope is built, the SHA-256 hash is computed, the ed25519 signature is added.
2

Hash queues for notarization

If the source account has notarization opted in, the UTR hash is queued. The queue runs every five minutes (Vercel cron).
3

Memo posted to Solana mainnet

The cron picks up unnotarized hashes, batches them into one or more memo transactions on Solana mainnet via the SPL Memo Program, and waits for confirmation.
4

Proof recorded

Once confirmed, the memo’s transaction signature, slot, and posting timestamp are stored alongside the UTR in utr_notarizations.

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Verifying a notarization

curl https://www.tradallo.com/api/v1/utrs/<utr_hash>/notarization
Returns a signed envelope: 
{
  "v": 1,
  "kind": "notarization",
  "utr_hash": "sha256:b81f…",
  "chain": "solana-mainnet",
  "signature": "5VzN…",
  "slot": 287123456,
  "posted_at": "2026-04-30T17:25:00Z",
  "explorer_url": "https://explorer.solana.com/tx/5VzN…",
  "envelope_signature": {
    "alg": "ed25519",
    "key_id": "tradallo-2026-04",
    "value": "MEUCIQDx8…"
  }
}
The explorer_url gives anyone a one-click way to confirm the memo transaction exists on Solana, contains the expected hash, and was confirmed at the expected slot.

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Why Solana

Three reasons:
  1. Memo program is a first-class primitive — no smart contract to deploy, audit, or upgrade. The instruction is Memo(bytes); the bytes are the UTR hash. Minimal attack surface.
  2. Sub-second finality — confirmations land in 1-2 seconds, so the notarization is bounded by the cron interval (5 min), not the chain.
  3. Sub-cent cost — even at scale, posting one memo per UTR is in the single-digit-dollar-per-month range. No batching tricks required.

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What it doesn’t do

On-chain notarization does not:
  • Reveal the trade. Only the hash is on-chain — the trade itself stays in Tradallo’s database. An observer of Solana sees a 32-byte hash, not your symbol/size/PnL.
  • Prove the trade is correct. It proves the trade existed at slot N. The signature on the UTR is what proves Tradallo asserts it’s a real trade.
  • Make the trade reversible. UTRs are immutable in either direction — once the hash is on-chain, removing it is not possible.
Opting out of on-chain notarization keeps the trade fully verifiable via the ed25519 signature. Notarization is a stronger guarantee, not the baseline guarantee.