Finality

Decentralized and Fault Tolerant

Finality is the affirmation that all well-formed blocks will not be revoked once committed to the blockchain. The chain is not subject to the risk of reorganization further back than the most recent block that achieved finality. On the Syscoin network, all nodes recognize finalized blocks as valid and accepted. Any nodes with chains that differ further back than the last chainlock are not accepted as valid peers on the network.

Syscoin’s finality uses chainlocks which are sourced from a multi-quorum consisting of 4 groups of 400 masternodes (1,600 total). These quorums are randomly selected among the entirety of Syscoin's network of masternodes (currently ~2,500 at time of documenting). Each quorum is reformed every few hours. 3 out of 4 quorums must agree on a block in order to establish a chainlock.

This mechanism provides a high probability of finality in a decentralized way, and fault tolerance is inherited from the underlying Nakamoto consensus. In the rare event that finality cannot be achieved on a block, the network falls back to the longest chain rule - a seamless and non-breaking event.

	Time to finality after block	Blocktime	Resilience absent finality	Mechanism
Syscoin	~12.5 minutes	2.5 minutes	Nakamoto longest chain rule	PoW + Quorums
Ethereum	~14 minutes (~3 epochs)	10 seconds	None. No finality = breaking event	PoS + Casper

This provides effective resistance to 51%, malicious long-range MEV, and selfish mining attacks, while retaining PoW as the underlying consensus mechanism. Attackers must accomplish two expensive and challenging tasks to achieve a successful 51% attack: 1) Control greater than 50% of Bitcoin's hash power supplied to Syscoin, plus 2) Control a super-majority of Syscoin masternodes.

Chainlocks can be viewed by using Syscoin Core RPC getchainlocks.