Masternode Quorums

Dash's masternode quorums are used to facilitate the operation of masternode provided features in a decentralized, deterministic way. The original quorums (used largely for InstantSend and masternode payments) were ephemeral and used for a single purpose (e.g. voting on one specific InstantSend transaction).

Dash Core 0.14 (protocol version 70214) introduced the Long-Living Masternode Quorum (LLMQ) system described in detail by DIP6. These LLMQs are deterministic subsets of the global deterministic masternode list that are formed via a distributed key generation (DKG) protocol and remain active for a long periods of time (e.g. hours to days).

The main task of LLMQs is to perform threshold signing of consensus-related messages (e.g. ChainLocks).

LLMQ Creation (DKG)

The following table details the data flow of P2P messages exchanged during the distributed key generation (DKG) protocol used to establish an LLMQ.

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Intra-Quorum Communication

Note: With the exception of the final step (qfcommit message broadcast), the message exchanges happen only between masternodes participating in the DKG process via the Intra-Quorum communication process described in the DIP.

Quorum DKG Data Flow

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Minimum Masternode Protocol Version

As of Dash Core 0.16.0, masternodes perform a version check on their quorum peers during DKG. Masternodes that do not meet the MIN_MASTERNODE_PROTO_VERSION (70223 in Dash Core 18.0) will begin receiving increases in PoSe score once 60% of the masternodes on the network have upgraded to that version.

MasternodeDirectionPeersDescription
Initialization PhaseDeterministically evaluate if quorum participation necessary
Each quorum participant establishes connections to a set of quorum participants as described in DIP6
Contribution PhaseSend quorum contributions (intra-quorum communication)
inv message (qcontrib)β†’Masternode sends inventory for its quorum contribution to other masternodes in the quorum
←getdata message (qcontrib)Peer(s) respond with request for quorum contribution
qcontrib message→Masternode sends the requested quorum contribution
Complaining PhaseSend complaints for any peers with invalid or missing contributions (intra-quorum communication)
inv message (qcomplaint)β†’Masternode sends inventory for any complaints to other masternodes in the quorum
←getdata message (qcomplaint)Peer(s) respond with request for quorum complaints
qcomplaint message→Masternode sends the requested complaints
Justification PhaseSend justification responses for any complaints against own contributions (intra-quorum communication)
inv message (qjustify)β†’Masternode sends inventory for any justifications to other masternodes in the quorum
←getdata message (qjustify)Peer(s) respond with request for quorum justifications
qjustify message→Masternode sends the requested justifications
Commitment PhaseSend premature commitment containing the quorum public key (intra-quorum communication)
inv message (qpcommit)β†’Masternode sends inventory for its premature commitment to other masternodes in the quorum
←getdata message (qpcommit)Peer(s) respond with request for quorum premature commitment
qpcommit message→Masternode sends the requested premature commitment
Finalization PhaseSend final commitment containing the quorum public key
inv message (qfcommit)β†’Masternode sends inventory for its premature commitment to all peers
←getdata message (qfcommit)Peer(s) respond with request for quorum final commitment
qfcommit message→Masternode sends the requested final commitment

LLMQ Signing Session

The following table details the data flow of P2P messages exchanged during an LLMQ signing session. These sessions take advantage of BLS threshold signatures to enable quorums to sign arbitrary messages. For example, Dash Core 0.14 uses this capability to create the quorum signature found in the clsig message that enables ChainLocks.

Please read DIP7 LLMQ Signing Requests / Sessions for additional details.

LLMQ Signing Session Data Flow

MasternodeDirectionPeersDescription
Siging Request PhaseRequest quorum signing of a message (e.g. InstantSend transaction input) (intra-quorum communication)
qsigsesann message→Masternode sends a signing session announcement to other masternodes in the quorum
Share Propagation PhaseMembers exchange signature shares within the quorum (intra-quorum communication)
qsigsinv message→Masternode sends one or more quorum signature share inventories to other masternodes in the quorum
May occur multiple times in this phase
←qgetsigs message (qcontrib)Peer(s) respond with request for signature shares
May occur multiple times in this phase
qbsigs message→Masternode sends the requested batched signature share(s)
May occur multiple times in this phase
Threshold Signature Recovery PhaseA recovered signature is created by a quorum member once valid signature shares from at least the threshold number of members have been received
qsigrec message→Masternode sends the quorum recovered signature to all peers (except those that have asked to be excluded via a qsendrecsigs message)

Note the following timeouts defined by Dash Core related to signing sessions:

ParameterTimeout, secDescription
SESSION_NEW_SHARES_TIMEOUT60Time to wait for new shares
SIG_SHARE_REQUEST_TIMEOUT5Time to wait for a requested share before requesting from a different node
SESSION_TOTAL_TIMEOUT300Time to wait for session to complete

Quorum Configuration

Mainnet and Testnet only use quorums of pre-defined sizes that are hard coded into Dash Core. RegTest and Devnet environments each have a quorum that supports custom size and threshold parameters that are controlled via command line or configuration file parameters (llmqtestparams/llmqdevnetparams).

A list of all the quorums and their default sizes can be found in the Current LLMQ Types table found in DIP-6.

The specific quorum type used for a feature can vary based on the network. The following table shows which quorums are used for each feature on the various networks:

MainnetTestnetDevnet *RegTest *
ChainLocks (DIP-8)LLMQ_400_60LLMQ_50_60LLMQ_50_60LLMQ_TEST
Deterministic InstantSendLLMQ_60_75LLMQ_60_75LLMQ_60_75LLMQ_TEST_DIP0024
InstantSend (pre DIP-24)LLMQ_50_60LLMQ_50_60LLMQ_50_60LLMQ_TEST_INSTANTSEND
PlatformLLMQ_100_67LLMQ_100_67LLMQ_100_67LLMQ_TEST
Enhanced Hard Fork (DIP-23)LLMQ_400_85LLMQ_50_60LLMQ_50_60LLMQ_TEST

* Note that the quorum types used on RegTest and Devnets have customizable parameters as described above

Quorum formation

The quorum formation process operates regardless of quorum usage. So the DKG process will be attempted for all quorum types enabled on a network regardless of whether or not that quorum type is going to be used.

The following table showing which quorums are enabled for each network type is derived from information taken from Dash Core's chainparams.cpp file:

Quorum typeMainnetTestnetDevnetRegTest
LLMQ_50_60xxx-
LLMQ_60_75xxx-
LLMQ_400_60xxx-
LLMQ_400_85xxx-
LLMQ_100_67xxx-
LLMQ_DEVNET--x-
LLMQ_DEVNET_DIP0024--x-
LLMQ_TEST---x
LLMQ_TEST_INSTANTSEND---x
LLMQ_TEST_V17---x
LLMQ_TEST_DIP0024---x

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