Zcash market listings

Universe Wallet implements listing signatures for the Universe market’s signed-order protocol, ZMarket Orders v1: a fixed-price offer to sell a Zerdinal inscription.

One signature, one exact outcome

A listing is a single signature under SIGHASH_SINGLE | ANYONECANPAY over a Zcash transaction digest computed from the listing terms alone. It binds your asset outpoint to exactly one outcome: any transaction that spends that outpoint must pay your own address the exact listed price. Everything else about the final settlement is the buyer’s to build, and your signature deliberately does not constrain it.

There is no escrow and no service custody. The market cannot move your asset, and equally your signature cannot choose the buyer: anyone holding it can settle the offer by paying you.

What the wallet checks before showing the approval

The request contains exactly the listing terms and optional asset evidence. Any other field is rejected before anything is reviewed.
The seller address is the connected account’s own Zcash address, and the payout script pays that same address, so the wallet never authorizes a sale of someone else’s asset or a payout to anyone else.
The network in the terms matches the active wallet chain.
The pinned consensus branch matches the network’s next block, so the listing becomes invalid by construction across a network upgrade.
The price is above the relayable floor, and the platform fee amount and fee script are consistent with each other.

Why the approval can be blocked

The signature sells everything the listed outpoint carries, so the wallet requires an asset verdict for that outpoint before it lets you approve.

An outpoint with no asset verdict blocks the approval, because what the signature would sell cannot be shown.
A verdict that does not carry the listed asset blocks the approval and names the mismatch.
An outpoint carrying more than the listed asset is shown in full, because a sale delivers all of it together.

Blocked is not a warning you can click through. The approve control stays disabled and the screen states the reason in the same words the wallet enforces.

The three consequences of approving

A listing is a public offer. Anyone can settle it at exactly these terms.
Cancellation is advisory. Cancelling removes the listing from the market. The signature stays valid until the asset moves or the expiry block passes. The only certain revocation is transferring the asset to yourself.
The ZEC riding on the asset outpoint transfers to the buyer with the asset. Set the price with that in mind.

The screen also shows the exact amount you are paid, the platform fee, which the buyer pays, the block at which the offer dies, the consensus branch, the outpoint being committed, and the digest the signature is over.

After you approve

Approval alone signs nothing. The wallet re-reviews the exact terms after your approval and before any key material is touched, and checks the consensus branch against the network again. If the terms no longer match what you saw, or the asset can no longer be verified, the wallet refuses instead of signing.