In mid-2014, an unknown perpetrator launched the famous Sybil attack (in combination with the traffic confirmation attack) on the anonymous Tor network for several months which was first noticed in January of 2014.

The cryptocurrency world has witnessed its fair share of high profile attacks on different Blockchain and projects in recent years.

Cyber attacks like 51% attack, hard fork attacks are known within the crypto world. 

We’ll be exploring the Sybil Attack highlighting its meaning, mode of operation and how to prevent such attacks.

What is the Sybil Attack?

The Sybil attack is a computer security attack that destroys the network by creating multiple identities (account, nodes or computer). For instance, one person creating different accounts on the blockchain. 

The susceptibility of the network to Sybil attacks depends on how low the cost of generating an account is, the extent to which the network accepts input from entities that it does not link to the chain of trusted entities, and whether the network is correct, all entities are treated equally. 

Sybil as a word was first gotten from a book that studied a woman diagnosed with a dissociative identity disorder. Sybil attacks are also called sockpuppetry.

Sybil Attackers Mode of Operation

• Sybil attacks can cause false resource sharing, lack redundancy, less reliability and lack of integrity on the blockchain network.

Entities in peer-to-peer networks use multiple identities for purposes of redundancy, resource sharing, reliability and integrity.

The attacker can present multiple identities to the peer-to-peer network in order to appear and function as multiple different nodes. Therefore, unfavourable factors can gain disproportionate control over the network, for example by influencing the voting results.

• When the attacker successfully controls the majority of the network computing power or hash rate. He may decide to change the arrangement of transactions, and prevent transactions from being confirmed. The attacker may also reverse transactions that he made while in control, which can lead to double-spending.

How the Blockchain Can Help Prevent Sybil attack

• Identity Verification

Identity-based verification technologies often offer accountability at the expense of anonymity, which can be an unfavourable compromise, especially in online forums that want to enable censorship-free information sharing and open discussion of sensitive issues. Verification authorities can try to protect user anonymity by denying reverse lookups, but this approach makes verification authorities the main target of attacks.

• Economic cost

The imposition of economic costs as an artificial entry barrier can be used to make Sybil attacks more expensive. For example, a proof of work requires users to show that they spent a certain amount of computational effort solving password problems. This helps to defend against its attack. 

Bitcoin’s blockchain uses a specific set of rules for generating new blocks. One of the rules is that the ability to create blocks must be proportional to the overall processing power of the proof-of-work mechanism. This means that you actually need to have the computing power to create a new block, making it difficult and costly for an attacker to do.

Because Bitcoin mining is so intense, miners have very strong motivation to keep mining honestly instead of trying to carry out Sybil attacks.

• Use of Sybil Specific Application

Many applications have been developed with a view to protecting against Sybil attacks. Examples are Whānau, I2P’s implementation of Kademlia SumUp and DSybil.

Conclusion

Although there have been no 100 percent defense mechanisms for Sybil attacks, over the years Sybil attacks on blockchain have reduced significantly.