id	author	title	date	pages	extension	mime	words	sentences	flesch	summary	cache	txt
blog-dshr-org-397		DSHR's Blog: A Note On Blockchains			.html	text/html	1718	334	81	DSHR's Blog: A Note On Blockchains Blockchains have three components, a data structure, a set of replicas, and a consensus mechanism: The role of the consensus mechanism is to authorize changes to the data structure, and prevent unauthorized changes. BFT requires a closed replica set, and synchronized operation of the replicas, so can be used only in permissioned blockchains. If joining the replica set of a permissionless blockchain is free, it will be vulnerable to Sybil attacks, in which an attacker creates many apparently independent replicas which are actually under his sole control. Defending against Sybil attacks requires that membership in a replica set be expensive. is that the security of the blockchain is linear in the amount of expenditure on mining power, ... The difference between permissioned and permissionless blockchains is the presence or absence of a trusted authority controlling the replica set.	./cache/blog-dshr-org-397.html	./txt/blog-dshr-org-397.txt