Umbra

Umbra is a private, non-custodial OTC venue for block trades built on the Canton Network, designed as a dark request-for-quote system. A buyer privately asks chosen dealers to price a block, and the dealers are blind to one another: a rival's quote is never sent to a competing dealer, because Canton withholds it at the ledger rather than in the frontend. The winning trade settles atomically as delivery-versus-payment, so there is no settlement risk, no escrow and no moment where one side has delivered and the other has not, and no quote or order leaks to losing dealers or the market. Its design uses Daml contracts for private swap requests, one invitation per dealer, a request desk that invites every dealer in a single signature, firm quotes with the payment and fee already locked, and an on-ledger dealer directory signed by each dealer. Umbra uses CBTC as a settlement asset and supports atomic swaps against cETH. It was built by a solo developer and finished second overall at HackCanton Season 2, also placing second in both the CBTC and cETH challenges, winning 15,000 CC.