Umbra Privacy

Umbra Privacy is a privacy protocol on Solana. Users connect a Solana wallet, register, deposit supported tokens into a shielded pool and hold a private balance, from which they can pay other registered users privately or withdraw to any Solana address; SOL and approved Solana tokens are supported. The project sold its UMBRA token on MetaDAO in October 2025, raising USD 3 million from commitments of USD 154.9 million. Its Private Mainnet went live on 2 February 2026 as the first application on the Mainnet Alpha of Arcium, a network for computation on encrypted data, with 100 new users a week and a deposit limit of USD 500, and its wallet opened to the public on 27 March 2026. On 23 October 2026 the address of Umbra's documentation redirected to docs.nimbusprivacy.xyz, which describes the protocol under the name Nimbus.

A private balance is the user's share of the tokens held by the pool's Solana program, so the chain shows the pool's holdings rather than each user's balance, and the user's device works its balance out from encrypted records. Depositing moves tokens from the user's wallet into the pool, and the wallet, token and amount are public. To pay someone, the device builds a proof that the user owns what they spend and that the payment creates no extra tokens, and a relayer submits the transaction to Solana, though users can submit it themselves; the sender, recipient and amount cannot be read from it, while the transaction, its timing and its relayer are public, and a paid relayer tip shows its amount and token. A withdrawal shows its destination, token and amount, but a relayed withdrawal does not show which private balance paid. The keys come from the user's wallet, and without it nobody, the developers included, can rebuild them.

The Block described the public wallet in March 2026 as built on Arcium's encrypted execution engine, with shielded transfers, encrypted swaps that do not reveal trade size, and an SDK for other developers; in May 2026 Umbra and Streamflow added private token vesting, each schedule joining Umbra's shared anonymity pool. The pages of the documentation read on 23 October 2026 do not mention Arcium: they describe guardian node clusters, a fee enclave whose code is checked against Amazon Web Services' root of trust, a screener and zones.

Umbra is built with compliance checks. The screener checks the public parties of each transaction and can refuse to sign it, and the homepage names Range and Cipherowl as examples of screening providers for public wallet addresses; every private transfer must go to a registered recipient that meets what the homepage calls KYP requirements, users can disclose chosen transaction details, and The Block listed viewing keys, risk screening and geo-blocking among the wallet's tools. A zone authority signs for notes entering and leaving its zone and can freeze that zone. Each governed operation has its own authority key: governance can change the accepted tokens, the fee rate, capped at 500 basis points, the screener keys and the zones, through public proposals with delays, but cannot move funds, spend notes without a valid proof or change the proof keys, and there is no switch that pauses the whole pool. Each program's Solana upgrade authority, however, can replace its code in a single transaction with no timelock, and operators can stop ordinary payments by taking a required service offline.