# Consensus A signature proves that an account's key authorized an action. It does not stop the owner from signing two conflicting payments that spend the same money. Nodes need to agree which payment happened, or two recipients could each believe they had been paid. That agreement is called consensus. BURST gives each account its own chain of signed entries, called blocks. Representatives vote when entries compete. A receive also points back to the payment it accepts, so confirming one account's history can depend on another's. This page explains that agreement process and why enough voting weight must remain online for it to continue. The minimum voting weight needed for a decision is called its **quorum**. ## Competing blocks Suppose Alice signs two different blocks after the same last confirmed block. They compete for the same position in her account history. Both cannot become her next confirmed block, even if both carry her valid signature. Representatives vote on candidates; confirmation requires the applicable final-vote weight and durable handling of the block's dependencies. Each verified account contributes one equal unit to its chosen representative. Token balances and creator status add no weight. The protocol depends on human verification to make those accounts correspond to distinct people. In the certified payment path, the installed checkpoint fixes the electorate, representative weights, payment epoch and quorum. Local peer availability does not shrink that electorate. The election helper defaults to 67%, rounded upward in integer arithmetic; the installed authority supplies the actual threshold. Representatives persist final-vote commitments. Restart is not permission to sign a conflicting final vote at the same position. Preserve signing journals alongside keys and ledger state; see [node recovery](../node/NODES.md). ## Representatives and delegation A representative receives voting weight when verified humans delegate to its address. There is no separate registration operation. To sign, its operator must run a node with the matching key and voting enabled. There is no principal-only voting threshold. A representative change has no dedicated cooldown, but certified payment weights change only when the new roster is certified and installed. An offline representative's weight stays in the quorum denominator. There is no automatic fallback, and changing delegation cannot bypass the quorum needed to install a successor. If too much weight goes offline, the network can stop advancing. ## Election lifecycle An election starts passive and becomes active when it accepts a vote. Soft votes can be replaced by later signed sequences. Once a representative's final vote is accepted, that election rejects any replacement. The lead in combined soft and final weight controls when final voting can begin; confirmation counts final votes only. Confirmed and expired are terminal election states. The node processes durable cementation separately. Its repair pass expires unresolved elections after five minutes, but expiry does not erase a representative's persisted voting commitments. ## Which candidates run first The node queues election candidates by their block's recorded TRST balance, with larger balances first and hash order breaking ties. This affects admission under contention, not representative weight or the confirmation threshold. A bounded ledger scan rediscovers unconfirmed account positions when work must wait or the node restarts. Votes can arrive before their candidate block. A bounded cache retains some of those authenticated votes until the candidate is validated and registered. Replay assigns weight from the election's frozen roster; a cached weight is not authority. Cache eviction can lose a vote, so this cache is not durable evidence of finality. ## Durable cementation **Cementation** is the node's process for permanently recording a block and its dependencies as confirmed. It is a storage step after voting. After final-vote confirmation, the node records pending confirmation durably. A background worker walks dependencies and advances each account's confirmation height without gaps. It commits confirmed authority and applicable governance state with that progress. Rollback cannot cross the confirmation height. One transaction handles up to 256 targets and cements up to 4096 blocks, with a 131,072-entry dependency traversal bound. Larger cuts continue in later batches. If an implicit dependency still needs its own quorum, the group defers without committing its staged writes. Confirmation therefore does not promise immediate cementation or a fixed finality latency. ## Signed votes and conflicting signatures Wire votes contain one to eight candidate hashes. Their signature covers the voter, final-vote flag, timestamp and sequence as well as those hashes, under the BURST vote domain. The receiver still needs the candidate blocks and their validated dependencies. A signature alone does not make a candidate valid. The node reserves local final-vote commitments before signing and refuses to replace an accepted final vote within an election. The standalone equivocation helper is not connected to this voting path. It stores conflicting hashes without signatures, so it cannot provide a proof for peers or establish a network-wide penalty. Soft-vote changes are allowed and must not be treated as conflicting final signatures. ## Shared checkpoints Account chains alone do not agree on a verifier pool, human roster, governance result or identity outcome. Certified checkpoints bind those shared decisions to an agreed ledger cut and parameter context. Existing authority authenticates its successor. A proposed new roster cannot establish its own legitimacy merely by signing with the voters it lists. Ordinary actions also name their payment epoch, so an old signature cannot be silently reinterpreted under a new authority context. If the necessary quorum is unavailable, progress can stop. Discarding vote locks or counting only reachable voters is not a valid recovery shortcut. For the replay, signing, installation and recovery contracts, see [checkpoints and state transitions](CHECKPOINTS.md). ## Verifier selection Selection first commits to the request, eligible pool, committee size, ledger cutoff, parameters and future beacon round. Only then can the agreed randomness be used. Choosing a pool after seeing the output would give the proposer a way to influence the selected panel. Drand supplies a verifiable beacon. BURST verifies its pinned chain policy and proof; an HTTP relay only delivers the data. Drand does not determine eligibility or certify BURST's identity judgments. The certified selection path validates the checkpoint certificate and exact beacon round, scores each eligible address with the verified random output, then sorts scores with address order as the tie-breaker. Identical inputs produce the same committee. For a pool of P accounts, this scoring/sorting step takes O(P log P) work; checkpoint replay and certificate verification add their own costs. If the agreed output is unavailable, the finalized request waits for that same round. Another relay can supply it, but the node cannot substitute local randomness, a different pool or a convenient later round. An unagreed proposal, a prepared proposal and a finalized selection have different recovery obligations. Consensus recovery must retain prepared evidence and vote locks; elapsed time alone cannot erase evidence held by another participant. These mechanisms do not constitute a proof against every scheduling or economic attack. ## Experimental randomness helper `vrf::commit_reveal` is a local transcript helper, not the node's production beacon. It seals the commitment set and requires every participant to reveal. A participant withholding a reveal prevents output. The helper does not implement authenticated network membership, deadline agreement or distributed recovery; it cannot replace the drand selection path on those terms. ## Availability The current certified-selection gate is disabled on Live. Experimental builds can enable the path on Test and Dev. These implementation rules are not a claim that a Live deployment or release has been qualified. See [verification availability](VERIFICATION.md#network-availability). ## Implementation - [Signed block fields](https://github.com/BURST-UBI/protocol/blob/main/ledger/src/state_block.rs) - [Installed payment authority](https://github.com/BURST-UBI/protocol/blob/main/node/src/payment_authority.rs) - [Election threshold arithmetic](https://github.com/BURST-UBI/protocol/blob/main/consensus/src/election.rs) - [Durable voting](https://github.com/BURST-UBI/protocol/blob/main/node/src/durable_votes.rs) - [Certified selection request](https://github.com/BURST-UBI/protocol/blob/main/verification/src/selection_request.rs) - [Experimental commit-reveal transcript](https://github.com/BURST-UBI/protocol/blob/main/vrf/src/commit_reveal.rs) - [Exact-round beacon retrieval](https://github.com/BURST-UBI/protocol/blob/main/node/src/checkpoints/beacon.rs)