[Retracted] A Comprehensive Survey on Sharding in Blockchains

Table 2

A comprehensive comparison of considered blockchain scalability solutions.

Parameter		Monoxide	Elastico	OmniLedger	RapidChain		Chainspace	Ethereum 2.0	TEEChain
Network model (S: synchronization; PS: partial synchronization; AS: asynchronization)		PS	PS	PS	Intra	S	PS	PS	PS
					Total	PS
Randomness	Existence	No	Yes	Yes	Yes		Unknown	Yes	Yes
	Use	N/A	(1) The seed of PoW puzzle for the next epoch; (2) select the leader during intrashard consensus	(1) Select the leader and the subgroup allocation; (2) epoch reconfiguration; (3) trust-but-verify transaction validation scheme	(1) The seed of PoW puzzle for the next epoch; (2) select the leader during intrashard consensus; (3) decentralized bootstrapping; (4) epoch reconfiguration		Unknown	(1) Select the proposer and attesters of each shard; (2) select the validators responsible for checkpointing from the global pool	(1) Decentralized bootstrapping; (2) epoch reconfiguration
Participants	Node allocation	Address-based one-off allocation	PoW-based allocation	-based allocation	PoW-based allocation		Object-based one-off allocation	-based allocation	-based allocation
	Safe epoch reconfiguration	N/A	Unsafe	Yes, at a given time	Yes, swapping out a constant number of node		N/A	Yes	Yes,
Transaction data structure		Account-based	UTXO-based	UTXO-based	UTXO-based		Object-driven, contract-sharded	Account-based	General workload
Global blockchain		No	Yes	Yes	Yes		No	Yes	Yes
Intrashard consensus algorithm		PoW-based Chu-ko-nu mining	PBFT	ByzCoinX	50% BFT		Mod start PBFT	BFT-based PoS	TEE PBFT
Security model	Threat model	Arbitrarily, uncoordinated majority	Arbitrarily, slowly adaptive	Arbitrarily, slowly adaptive	Arbitrarily, slowly adaptive		Arbitrarily, uncoordinated majority	Arbitrarily, uncoordinated majority	Arbitrarily, uncoordinated majority
	FT; Intrashard
	Global
Cross-shard Tx	Support or no	Support	No	Support	Support		Support	Support	Support
	Method (S: synchronization; AS: asynchronization)	AS, lock-free	N/A	S, lock, or unlock	S, lock, or unlock		S, lock, or unlock	S, lock, or unlock	S, 2PC, and 2PL
Complexity	Communication	Mixed: Identical:
	Storage