Mapping out Sybil Resistance Mechanisms

One of the biggest risks for decentralized networks is Sybil attacks. In a Sybil attack, an attacker creates a large number of accounts to trick a network into thinking that several individual accounts are participating in the network, when in fact they are all controlled by the attacker. The attacker then leverages these accounts to exert influence on the network in variety of ways: manipulating the reputation system of an e-commerce shop, obtaining a disproportionate share of a network's resources, etc. 

To avoid Sybil attacks, centralized networks set rules and approval measures for accounts that want to participate in the network. Decentralized networks, however, are particularly prone to Sybil attacks due to their permissionless nature: any individual can participate in their networks. As a past example, attackers have performed versions of Sybil attacks on popular P2P networks like BitTorrent.