Sybil Resistance

A sybil resistance mechanism that requires participants to expend significant computational energy to validate transactions and create new blocks. The high cost of electricity and specialized hardware (ASICs) acts as a barrier to creating multiple fake identities.

• Example: Bitcoin and Ethereum's original consensus algorithm.
• The security model assumes that an attacker would need to control >51% of the network's total hashing power, making a Sybil attack economically irrational.

A sybil resistance mechanism where validators are required to stake or lock a significant amount of the native cryptocurrency. The right to propose or validate blocks is weighted by the size of the stake. Attempting a Sybil attack requires acquiring a majority of the staked asset, which is both costly and would devalue the attacker's own holdings.

• Example: Ethereum 2.0, Cardano, Solana.

A mechanism that uses biometrics or government-issued IDs to cryptographically verify that each participant is a unique human. This directly attacks the Sybil problem by tying one identity to one person.

• Projects: Worldcoin (orb iris scans), BrightID (social graph verification).
• Used for fair airdrops, quadratic funding, and governance where 'one-person-one-vote' is essential.

A decentralized method where identities are validated through attestations from other trusted participants, forming a network of verifications. Creating a Sybil identity requires infiltrating this trust network, which becomes difficult at scale.

• Concept: Used in decentralized identity protocols like Veramo and Ceramic.
• Often combined with other mechanisms for scalable, privacy-preserving verification.

Imposing a small but non-zero cost for actions or limiting the rate of actions from a single entity. This makes large-scale Sybil attacks economically unviable or too slow to be effective.

• Examples: Gas fees on Ethereum for transactions, CAPTCHAs for website access, cooldown periods in governance votes.
• Effective for protecting against spam and ensuring fair access to resources.

A concept where non-transferable tokens (Soulbound Tokens) are issued to a unique cryptographic identity (a 'Soul'), representing credentials, memberships, or attestations. This creates a persistent, composable identity that results in plurality—a system where identity is based on multiple, verifiable sources.

• Proposed by: Vitalik Buterin, E. Glen Weyl, and Puja Ohlhaver.
• Aims to move beyond simple token-weighted voting to more nuanced, Sybil-resistant governance.

Proof of Work requires miners to expend significant computational energy to solve cryptographic puzzles. This creates a tangible, real-world cost for creating identities (mining nodes). A Sybil attacker would need to control more than 50% of the network's total hash rate, a prohibitively expensive feat for major chains like Bitcoin.

• Cost as a barrier: The electricity and hardware costs make creating fake nodes economically irrational.
• Example: Bitcoin's Nakamoto Consensus relies on this to secure the network and validate transactions.

Proof of Stake requires validators to lock up (stake) a significant amount of the native cryptocurrency. This creates a strong financial disincentive for Sybil attacks, as malicious behavior leads to slashing (loss of staked funds).

• Stake as collateral: To control the network, an attacker would need to acquire a majority of the staked tokens, making an attack extremely costly and self-defeating.
• Example: Ethereum, after The Merge, uses a PoS consensus mechanism where validators must stake 32 ETH.

Proof of Personhood protocols aim to cryptographically verify that each participant is a unique human, not a bot or duplicate. This is a direct counter to Sybil attacks in governance and distribution systems.

• Biometric verification: Projects like Worldcoin use iris-scanning orbs to generate a unique IrisHash.
• Social graph analysis: BrightID establishes uniqueness through verified social connections in video-chat parties, preventing a single user from creating multiple accounts.

Protocols design token distributions and governance to be Sybil-resistant. They use on-chain activity analysis and anti-sybil filters to identify and exclude duplicate or bot-controlled wallets.

• Activity-based criteria: Rewarding historical users based on transaction volume, frequency, and longevity.
• Example: The Uniswap UNI airdrop used complex criteria to distribute to past users while attempting to filter out Sybil farmers. Gitcoin Grants uses quadratic funding which is more resilient to Sybil attacks than simple voting.

In many Byzantine Fault Tolerant (BFT) consensus protocols, the validator set is permissioned or requires a high-cost entry barrier. This pre-vetting process inherently provides Sybil resistance by limiting who can participate in consensus.

• Known Identity: In consortium blockchains, validators are known, legally accountable entities.
• Bonded Security: Networks like Polygon POS and Cosmos require validators to bond substantial stake, making it costly to run many malicious nodes.

While not purely cryptographic, these are foundational web2 techniques adapted for blockchain interfaces to prevent bot spam and Sybil account creation.

• CAPTCHAs: Used by centralised exchanges (CEX) and wallet services during sign-up.
• Rate Limiting: Restricts the number of actions (e.g., API calls, free transactions) from a single IP address or API key, increasing the cost and complexity of mounting a Sybil attack on a service layer.

A consensus mechanism that requires participants to solve computationally expensive cryptographic puzzles to validate transactions and create new blocks. This creates a cost barrier to creating fake identities, as each Sybil attack would require immense, verifiable energy expenditure. The primary limitation is its massive energy consumption, which raises environmental and scalability concerns. Bitcoin is the canonical example.

A consensus mechanism where validators are chosen to create new blocks based on the amount of cryptocurrency they stake as collateral. Sybil resistance is achieved through economic disincentives; malicious actors risk having their staked assets slashed (destroyed). Limitations include potential centralization of stake among large holders and the "nothing at stake" problem in early implementations, which is mitigated by slashing penalties.

A Sybil-resistance method that aims to cryptographically verify that each participant is a unique human, not a bot or duplicate. This is often achieved through biometric verification or social graph analysis. A key limitation is the privacy trade-off, as it requires submitting personal data. Projects like Worldcoin use iris scanning, while others like BrightID analyze social connections to establish uniqueness.

A variant of PoS where token holders vote for a small set of delegates (or validators) to secure the network on their behalf. Sybil resistance is concentrated on these elected delegates, who have significant staked value and reputation at risk. The primary limitation is increased centralization pressure, as power consolidates around a small, known group of validators, potentially creating an oligopoly. EOS and TRON use this model.

A Sybil-resistance mechanism for creating trusted lists (e.g., of oracles, DAO members) where listing requires staking tokens. Challenges to listings are resolved through token-weighted voting. It resists Sybils by making attacks economically costly. Limitations include voter apathy, where token holders may not participate diligently, and the potential for wealth-based governance where the richest voters dominate list curation.

All Sybil-resistance mechanisms involve fundamental trade-offs:

• Cost vs. Accessibility: PoW/PoS cost barriers can exclude participants.
• Decentralization vs. Efficiency: More decentralized systems (PoW) are often slower; efficient systems (DPoS) are more centralized.
• Privacy vs. Verification: Proof-of-personhood sacrifices anonymity.
• Game Theory Reliance: Most mechanisms depend on rational economic actors, which can fail during market irrationality or sophisticated collusion attacks.

A Sybil resistance mechanism that requires participants to expend computational energy to validate transactions and create new blocks. The high cost of hardware and electricity makes it economically unfeasible to amass a majority of the network's hashing power, thereby preventing Sybil attacks. This is the consensus mechanism used by Bitcoin.

• Key Property: Economic cost as a barrier to entry.
• Example: An attacker would need to control >51% of the global Bitcoin hash rate to execute a Sybil attack, a prohibitively expensive endeavor.

A Sybil resistance mechanism that requires validators to lock up or 'stake' the network's native cryptocurrency as collateral. Influence is proportional to the amount staked, and malicious acts can lead to the slashing (loss) of the staked funds. This creates a strong financial disincentive for Sybil attacks.

• Key Property: Financial stake as collateral for honest behavior.
• Example: In Ethereum's PoS, a validator must stake 32 ETH. Creating multiple validator nodes requires proportionally more capital at risk.

A Sybil resistance mechanism that cryptographically verifies the unique identity of a human participant, often through biometrics or government ID. It ensures 'one person, one vote' in governance systems, directly countering Sybil attacks by linking influence to a verified human.

• Key Property: Unique human identity as the scarce resource.
• Example: Projects like Worldcoin use iris-scanning orbs to generate a unique proof of personhood, granting a global digital identity.

A self-sovereign identity standard (W3C) that allows individuals to create and control verifiable digital identifiers without relying on a central authority. DIDs can be a foundational component for Sybil-resistant systems by providing a portable, cryptographically verifiable identity anchor.

• Key Property: User-controlled, verifiable credentials.
• Example: A DID can be used to prove membership in a unique social graph or community without revealing personal data, aiding in reputation-based Sybil defense.

The practice of users creating multiple wallet addresses (Sybils) to illegitimately claim a larger share of a token airdrop. This is a direct manifestation of a Sybil attack against a distribution mechanism. Projects combat this by using Sybil detection algorithms that analyze on-chain behavior to filter out bot-like activity.

• Key Challenge: Distinguishing between organic users and coordinated Sybil clusters.
• Defense: Analyzing transaction graphs, gas spending patterns, and social connections.

A specific, critical failure of Sybil resistance in Proof of Work and Proof of Stake networks. It occurs when a single entity gains control of the majority of the network's mining hash rate or staked assets, allowing them to censor transactions, double-spend coins, and rewrite the blockchain's recent history.

• Relation to Sybil Attacks: A 51% attack is the ultimate goal of a successful Sybil attack on a consensus layer.
• Prevention: Relies on the high cost (PoW) or large stake (PoS) required to achieve majority control.