Sybil Attack Vector

What does Sybil Attack Vector mean?

A threat to blockchain integrity by a single entity that controls many validating nodes.

Main Idea:

It is possible for a person, entity, or nation state to have enough resources to pay for many nodes in a blockchain network. Multiple nodes that pretend to be independent, but are cooperating, are engaging in collusion. Multiple nodes controlled by one person or entity are called Sybils.

In a permissionless network, it may be difficult a priori to tell who is controlling what, so all permissionless blockchains remain quite vulnerable to a Sybil attack. A Sybil attack occurs when a malicious attacker controls enough nodes to alter the consensus on data that should go into the blockchain to its own advantage. The original double-spend problem in Satoshi Nakamoto’s White Paper was a type of Sybil attack vector that was addressed by the proposal of Proof of Work.*

Proposed Solutions:

Most blockchain protocols propose some mechanism to reduce the probability of a Sybil attack. These range from trying to make it very expensive to gain such an advantage, which is the essence behind the original Proof of Work and Proof of Stake proposals for permissionless blockchains.

For private blockchains that depend on Proof of Authority (meaning the nodes are identified and associated with nodes, who are often large corporations and have put reputations and resources on the line), the main line of defense against Sybiling is to hope that risks to reputation and working relationships within the consortium are enough to deter bad behavior. (Assuming resources are sunk costs.)

Other protocols introduce randomness, large networks, additional layers of validators, or governance. All of these arguably make it more difficult for a Sybil attack to be successful although ignore the problem of free riding. Nonetheless, if an entity is able to gather the requisite control needed over the relevant active set of actors then the Sybil attack vector continues to exist.

The threat or execution of a Sybil attack can be very disruptive and cause controversy over which blockchain ought to be the canonical (reference) blockchain database going forward. These controversies have occurred and split user communities. If the outcome is acceptable to all involved, the protocol may be fine for those uses. However, if a protocol is intended for businesses who would like to use blockchain to resolve disputes and uncertainty, then it would be wise to use a protocol that is invulnerable to these attacks.

*Other blockchain literature may refer to Sybil attacks as a broader category, including spamming the network. Spamming the network is typically deterred by requiring a transaction fee for each transaction sent, which is a variation on increasing the cost of a Sybil attack. The Sybil attack we present is the most often referenced example, although there may be differences in the way it is described.

Geeq’s Unique Solution:

Geeq’s Proof of Honesty-based blockchains are protected from Sybil attacks unless the attacker is able to take over the entire permissionless network (100% of validating nodes); at which point the network stalls and must restart with the Catastrophic Recovery Procedure. Proof of Honesty’s protection from Sybil attacks is called 99% BFT and is far higher than Proof of Work (a majority of hash power or 51%) and Proof of Stake (more than 1/3 of the stake).

A Sybil attack is a very elementary form of strategic attack. Proof of Honesty’s design makes use of decades of experience in game theory and economic mechanism design to design a protocol that results in strategically provable security, which is robust to more complicated attack vectors.

As mentioned above, even if a nation state is able to shut down a blockchain for a period of time, Proof of Honesty includes a procedure for every blockchain’s permissionless validation network to restart itself from the last honest Current Ledger State, to provides a clear, consistent and dependable reference for its users’ blockchain-based database.

Used in a Sentence:

A Sybil attack vector has a relatively high probability of success if the validation protocol depends on a consensus agreement as a pre-requisite for the determination of a canonical blockchain; Geeq’s Proof of Honesty achieves the maximum degree of security against these attacks.

Last Updated: February 25, 2023