Delegated-Proof-of-Stake as an altrnative to PoW and PoS: comparison and perspectives (p. 5)

Disadvantages of DPoS

Systems based on DPoS are criticized because of the de-anonymization of validators, the possible centralization of the production of units and the specificity of the control model.

Deanomization of validators

In DPoS systems, identity validators are known. Most often, these are not individuals, but companies that must maintain reputation and represent themselves to the voting members of the network in order to compete for the right to add blocks.

Given that the processing order of the blocks and the identity of the validators are known, the attacker can conduct a DDoS attack on the validators. The more validators are attacked, the more noticeable will be the network latency. However, the chances that an attacker could disable most of the nodes are small. In addition, validators can use DDoS resistance as a competitive advantage.

"The problem is that if you have 100 nodes, the system is much more centralized. You can conduct a DDoS attack on them. So how do you need to vote for them, those nodes that everyone knows will win. So much easier to attack people at the head of nodes. Internet providers, companies or governments can easily disable them. This particular approach
scalability is expensive: if you try to achieve scalability by increasing the size of individual nodes, the number nodes drops, the system becomes more centralized"


-explains Vitalik Buterin, founder of Ethereum

In response to Buterin’s statement, Daniel Larimer mentioned that Ethereum and Bitcoin had already been subjected to DDoS attacks, Steem and BitShares had survived despite attempts to overload the network. Larimer also clarified that the Ethereum network can be disabled by attacking just 7 nodes that control 90% of the computing power, and all of these nodes are well known to governments and Internet providers.

Centralization

Blockchain-based systems DPoS are called (https://cryptomaniaks.com/latest-cryptocurrency-news/blockchain/is-dpos-an-improvement-over-pos) more centralized from a point view of the total nodes that verify and add blocks. In NEO 7 validators work, and in Ethereum number of nodes exceeds 13,000.

On the other hand, you can not judge about the degree of centralization by one metric. In PoW-systems Ethereum and Bitcoin significant contribution to the creation of blocks several large mining pools.

Democracy problems

The decision on the choice of delegates-validators in DPoS is made by the network members. Theoretically, they can choose a validator with a good reputation, but with malicious intent. As soon as unscrupulous intentions are revealed, the voting members will exclude such a validator from the pool, but an attacker may have time to cause network disruptions.

"The problem is that the average voter has only small chance to influence the final list of delegates, because they have there is little motivation to vote on the basis of some idealistic goals. They more motivated to vote for those who offer the largest and reliable bribe"


-explains Vitalik Buterin, founder of Ethereum

As with any electoral system, the choice of validators in a DPoS network requires the attention of voters. Participants with a small number of tokens, and therefore a comparatively small influence on the outcome of the vote, are not motivated to spend time studying all the delegates.

"On-chain management makes node participation in management completely unnecessary. In this case, the node, without making decisions, simply follows made decisions. The default values are incredibly strong: what the more nodes follow these values, the less sense for interested in the change node go them in defiance and fork"


-explains Vlad Zamfir, a developer from Ethereum Foundation