Dark Pool Swap
The Swap page places dark pool orders. Both the amounts and the assets stay private — this is the strongest privacy Umbra offers.
Placing an order
- You’re Selling — pick the asset, then select one of your shielded
notes. The note’s full amount becomes the order’s
amountIn; orders consume a whole note. - You Want — pick the asset you want back.
- Minimum Acceptable Amount — your slippage floor. A match that would give you less than this cannot be proven, so it cannot settle.
- Confirm.
| Step | What happens |
|---|---|
| Generate ZK Proof | The place_order circuit runs in your browser |
| Submit Order | placeOrder() — the note’s nullifier is spent, the order commitment inserted |
| Confirm On-Chain | Wait for the OrderPlaced event and its leaf index |
| Self-Announce | A second confirmation — announces the order to yourself via StealthAnnouncer, so it’s recoverable from another device (see below) |
| Order Placed | Order details go to the matcher |
Two separate things happen
The on-chain placeOrder() call fully authorizes and places your order.
The order is real the moment that transaction confirms.
Handing the order’s private details to the matcher is a separate step afterward, and it only makes the order findable for matching. If the matcher can’t be reached, the app tells you so specifically — your order is on-chain, it just needs to be resubmitted for matching. It is not an “order failed” error, because nothing failed.
What’s public
Two values from placeOrder() itself: the spent note’s nullifierHash and
an opaque orderCommitment. Nobody watching the chain can tell what you’re
selling, what you want, how much, or at what limit.
The self-announce step adds one more public fact: an announcement to your
own wallet address, in the same block as the OrderPlaced event. That’s a
small new correlation that didn’t exist before it — someone watching the
chain can now link “this wallet placed an order around this time,” which
the placement transaction alone never revealed. It doesn’t disclose the
order’s contents, only that involvement. See Note Delivery
for why announcing to yourself uses the same mechanism as announcing to
someone else.
The matcher, who receives your order details off-chain, does know the contents. See the tradeoff note in Dark Pool Matching for exactly what that discloses.
Partial fills
Orders support partial fills. If a match only consumes part of yours, the leftover automatically re-commits as a smaller residual order under your own key, with the minimum scaled pro-rata.
You don’t have to do anything for a residual to keep working — it’s announced to you on-chain and re-listed on the matcher’s book immediately, so it’s live and matchable whether or not you’ve claimed it yet. Claiming just adds it to your view: it’ll show up under “Unclaimed residual orders” on this page’s My Orders tab, ready to claim into your own open-orders list.
How fills are priced
The backend sizes every fill against the live FTSOv2 rate, so the realized rate for the filled portion is the fair rate by construction rather than whatever the two order sizes happen to imply. If no valid fill clears both sides’ minimums at that rate, it refuses to propose one at all.
The circuit remains the actual authority — it independently checks that both sides’ pro-rata minimums are met. The FTSOv2 sizing is an off-chain policy layer on top, not the thing keeping you safe.
Cancelling
Open orders are listed on the same page. Cancel one and the cancel_order
circuit spends the order commitment and inserts a regular note commitment
back — the refund, for the original amount and asset, under your own key.
The refund is then self-announced too, the same reason and same tradeoff as
placing an order (above) — recoverable from another device, at the cost of
one more on-chain link between your wallet and this cancellation.
Cancelling reveals nothing about what the order contained. Only the nullifier, the refund note’s opaque commitment, and that self-announcement become public.
Waiting for a match
Neither trader needs to be online at match time. Once your order is on the book, the matcher can pair it and generate the proof without you. Matched proceeds arrive as a shielded note you claim on the Pay page’s Incoming tab — a partial fill’s leftover, if any, is claimed separately here on Swap instead, since it’s a residual order rather than a note.