5.3 Sybil Resistance Mechanisms

This section demonstrates from both economic and topological perspectives how OmniPact can defend against large-scale fake account attacks. We prove that in the OmniPact protocol, the cost of establishing fake reputations increases exponentially until it exceeds the potential malicious gains.

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In a decentralized pseudonym system, Sybil attacks—where attackers create a large number of fake identities to manipulate reputation or voting—are the biggest systemic threat. OmniPact abandons centralized authentication (such as uploading ID cards) and instead builds a defense system based on the "Cost of Forgery" and "Graph Analysis".

5.3.1 Cost-of-Forgery Analysis

Omni-ID's reputation score is not generated for free; it is forged by consuming real capital and time. Through protocol design, we have transformed "score trading" into an economically unsustainable and unprofitable activity.

1. Wash Trading Attrition Model

Attackers attempt to boost their reputation score through self-dealing. However, every transaction that generates valid reputation must incur a protocol fee (e.g., 0.5%) and a gas fee.

The total cost of forging a high-reputation accountDefined as:

$$C_{forge} = \sum_{i=1}^{N} \left( V_i \times R_{fee} + \text{Gas}_i \right) + \text{Cost}_{time}(Capital)$$

• Vi: The amount of the i-th order.

• Rfee:The fee charged by the protocol (this part of the funds will be recovered or destroyed by the national treasury, and is a pure expenditure for the attacker).

• Cost time: The opportunity cost of funds during the lock-up period (interest on funds).

Because the reputation score uses a logarithmic growth model, attackers must conduct a massive number of transactions to achieve a high score. As transaction volume accumulates, transaction fee attrition increases linearly, while reputation gains only increase logarithmically.

Ultimately, $C_{forge}$ will far exceed the potential profit $E_{profit}$ that the account could generate as a "fraudulent tool," making the attack economically unprofitable.

2. Proof-of-Funds Barrier

Only accounts that have completed a substantial transfer of value can gain credibility.

• The system filters out all "micro-dust transactions".

• Funds must be locked in the Vault for a period of time (time-weighted value). Quick-in-quick-out flash loan attacks cannot accumulate credit points.

5.3.2 Social Graph Verification

In addition to economic barriers, OmniPact also uses graph theory to identify the topological characteristics of witch accounts. Witch accounts typically exhibit "dense internal interconnections and sparse external connections," forming isolated subgraphs.

1. Trust Flow Algorithm

We introduce an iterative algorithm similar to EigenTrust++ or PageRank to calculate the global reputation weight.

$$T_{i} = (1 - a) \sum_{j \in In(i)} (c_{ji} \times T_{j}) + a \cdot p_{i}$$

• If account A has a very high reputation (e.g., the address of a well-known auditing firm), then the reputation of account B, which has transacted with A, will increase accordingly (trust transfer).

• Island Detection: If a group of accounts If a cluster only trades with each other internally and never interacts with existing high-reputation nodes (mainnet) in the network, the algorithm will identify it as a Sybil Cluster.

• De-weighting: The weight of transactions originating from within the witch cluster in the reputation calculation formula It will be downgraded to 0.

2. Web3 Identity Combination (Composable Identity Bootstrap)

OmniPact does not operate in isolation; we aggregate external DID (Decentralized Identity) signals as initial trust anchors:

• Gitcoin Passport: Reads the user's Gitcoin score.

• ENS / Lens Protocol: Analyzes users' social activity.

• Proof of Humanity: Verifies the status of a real person.

If a newly generated Omni-ID address has no history on the Ethereum mainnet (Nonce=0) and is not bound to any external DID, the system will automatically mark it as "High Risk" and impose a stricter "Slow Start" limit on its initial reputation accumulation, thereby further increasing the time cost of Sybil attacks.

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By combining "economic wear and tear" with "graph isolation," OmniPact has demonstrated that it can still construct a mathematically resistant and clean reputation network without relying on centralized KYC institutions.