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Ledger Engine

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UTXO Ledger Engine Specification
The UTXO Ledger Engine defines the logic for maintaining an immutable history of all deposits, trades, and settlements occurring on a Participating Interface. The latest state of the engine can be used to derive the balances of all traders with assets deposited on the PI.
Both PIs and SDPs must run an instance of the engine. SDPs must validate that UTXOs included as inputs and generated as outputs in all trades emitted by the PI are the result of correctly running the UTXO engine. Thus, the core logic of the engine must be deterministic, so that given the same order of deposits and trades, the PI and all servicing SDPs reach the same ledger state.
Configuration
MUST require user to specify whether the engine is being run by a PI or an SDP
SDP Operation
MUST provide an endpoint for the SDP to send a Trade and call the validateTrade function, responding with the result
PI Operation
MUST provide an endpoint for the PI to send a TradeParams and call the prepareTrade function, responding with the result
MUST provide an endpoint for the PI to send a Deposit and call the prepareDeposit function, responding with the result
MUST provide and endpoint for the PI to send a SettlementRequest and call prepareSettlement
MUST strictly sequence and process each StateTransition provided by the PI
Ledger Database
MUST store all UTXOs in a database, unhashed
MUST support querying UTXOs by any of their attributes
Functions
Note that every function defined below MUST be atomic.
validateTrade
Given Trade:
extract TradeParams and pass to determineTradeUTXOs
using the result of determineTradeUTXOs:
hash each input UTXO for side A
hash each input UTXO for side B
hash each output UTXO for side A
hash each output UTXO for side B
extract inputUTXOs and outputUTXOs from Trade
if hashes of input and output UTXOs generated match UTXO hashes in Trade, return true to indicate a valid trade
if UTXOs don't match, return false along with an UnsignedTrade with the correct input and output UTXOs
prepareTrade
Given TradeParams :
call determineTradeUTXOs with TradeParams
using the result of determineTradeUTXOs:
hash each input UTXO for side A
hash each input UTXO for side B
hash each output UTXO for side A
hash each output UTXO for side B
using TradeParams and the input and output UTXO hashes create an UnsignedTrade
append output UTXOs to the ledger
return the UnsignedTrade
prepareSettlement
Given SettlementRequest:
query for all unspent UTXOs with the same asset and trader to use as inputs
for all UTXOs above, generate a SettledUTXO to use as output
hash all input and output UTXOs
use SettlementRequest and UTXO hashes to create SettlementParams
return the SettlementParams
prepareDeposit
Given Deposit:
call hashDeposit
using Deposit and the result of hashDeposit, create a DepositUTXO
append the DepositUTXO to the ledger
return the hash of the deposit
determineTradeUTXOs
Given TradeParams:
determine TradeSide for trader that submitted Order a and call determineInputUTXOs
determine TradeSide for trader that submitted Order b and call determineInputUTXOs
use TradeSide and input UTXOs determined from Order a , and trader of Order b to call generateOutputUTXOs
use TradeSide and input UTXOs determined from Order b , and trader of Order a to call determineOutputUTXOs
return all input and output UTXOs
determineInputUTXOs
Given TradeSide:
query for all unspent UTXOs with same asset and trader as specified in the TradeSide, sorted descending by UTXO hash
iterate through UTXOs from the query result and add to a list until the sum of the amounts of the selected UTXOs is greater than or equal to the amount in the TradeSide
return the list of selected UTXOs
generateOutputUTXOs
Given TradeSide , list of input UTXOs, and address counterParty:
iterate through input UTXOs and generate symmetric output UTXOs
if the sum of the amounts in input UTXOs is greater than the amount in the TradeSide, then the final input UTXO will generate a second output UTXO granting the remainder to the counterParty
State Updates and State Transitions
UTXO DAG Description
Last modified 5mo ago