Liveness

Umbra stops more easily than it breaks. Every value transaction needs several independent signers, and any one of them can halt it by being offline. Funds are never at risk from that, and the escape hatch means a halt is never a trap.

What every value transaction needsCopy Anchor Link

Every deposit, transfer and withdrawal needs all six attesters to sign: the three guardian nodes, the screener, the fee enclave and the data endorser. There is no threshold, so if any one does not sign, the transaction cannot land. The guardian cluster must also be fully healthy, which it is not while a member is down, restarting or being replaced, or while the cluster is frozen.

When a part is unavailableCopy Anchor Link

• A guardian node or the cluster. No value transaction or registration lands until it is back.
• The fee enclave. No value transaction lands until it is back. Registration does not need it.
• The screener. No value transaction lands until it, or another registered screener, is back.
• The data endorser. No value transaction or registration lands until it, or another registered data endorser, is back.
• A relayer. Another relayer can carry your transaction, or you can submit it yourself.
• The indexer. Your client cannot build spends without the data it serves, though that data can in principle be rebuilt from the chain.
• The note archive. Recipients cannot find new notes until it is back.
• The forester. Spent-note records pile up in a staging buffer, and spending stops once it is full, after about 20,000 value transactions. Anyone may run a forester.
• Solana. Nothing lands.

The escape hatchCopy Anchor Link

The escape hatch takes one note out of the pool to a public address with no guardian node, screener, fee enclave, data endorser, zone signature or relayer, so it keeps working while they are down or frozen. It needs only your keys, the tree data and room in the staging buffer. The note is spent at once, and its payout is released after a 48-hour hold. In exchange, the exit makes the note's details public. See the escape hatch.

RelatedCopy Anchor Link