# HASC 2.0 Consensus Mechanism

HASC 2.0 (Hybrid Adaptive Secure Consensus 2.0) is the core consensus mechanism of the Arca Chain ecosystem, representing the latest advancements in blockchain consensus technology. This innovative hybrid adaptive secure consensus mechanism cleverly integrates the advantages of various consensus algorithms and introduces a layered structure and Task-weighted Proof of Stake (TwPOS) mechanism, providing unified security and efficient operational foundations for the entire multi-layer blockchain architecture.

#### 1. Principles and Mechanism

HASC 2.0 adopts a dual-layer structure comprising a core layer and an external layer to cater to the needs and capabilities of different types of nodes, applying different consensus mechanisms as needed in the core and external layers.

In the core layer, the nodes are primarily composed of Arca Mobile Secure Smartphones, which are the main participants and decision-makers of the core layer network. The core layer employs the Task-weighted Proof of Stake (TwPoS) mechanism combined with an improved Proof of Work (PoW). Participants in the core layer are mainly responsible for network governance, resource allocation, and critical decision-making.

In the external layer, it primarily includes a wide range of ordinary nodes and lightweight nodes (such as regular PCs or other mobile devices). The external layer adopts a simplified Proof of Stake (PoS) mechanism to accommodate large-scale node participation. The external layer is mainly used for asset transfers, on-chain transactions, and smart contract interactions.

#### 2. Task-weighted Proof of Stake (TwPoS) Mechanism

TwPoS is the primary consensus mechanism of the core layer. TwPoS not only relies on the number of tokens held by a node to determine its stake in the network but also assigns additional weight to nodes based on the completion of specific tasks assigned by the network. These tasks can take various forms, such as participating in mining, providing computing power, storage space, bandwidth, and other network resources, or even completing specific advertisement click tasks.

The formula for calculating the weight is:

{% code overflow="wrap" %}

```
W = α⋅S + β⋅T + γ⋅E

where:

S is the number of ARCA tokens held by the node;
T is the score of the tasks completed by the node;
E is an external variable representing the impact of sudden events or external conditions in the network;
α, β, and γ are the weighting coefficients for ARCA token holdings, task scores, and external variables, respectively, such that α + β + γ = 1.
```

{% endcode %}

The adaptive mechanism is one of the key features of HASC 2.0, allowing it to dynamically adjust various parameters based on network conditions and needs. This includes real-time adjustment of PoW difficulty based on the network’s hash rate and transaction volume, the use of verifiable random functions (VRF) combined with TwPoS weights for validator selection, and dynamic adjustment of the α, β, and γ values based on network requirements.

The external variable E accounts for the impact of external environments or sudden events on node weights. For example, during network attacks or specific challenges, certain tasks or resource contributions may receive additional weight due to emergency responses or special needs. By incorporating the external variable E, the TwPoS mechanism in Arca Chain can dynamically adjust node weight allocation to better adapt to complex and changing network environments, enhancing network resilience and responsiveness.&#x20;

#### 3. Enhanced Security, Cross-Layer Coordination, and Cross-Chain Interoperability

Enhanced security is one of the core objectives of HASC 2.0, achieved through multi-signature schemes, long-range attack protection, and fine-tuned incentive mechanisms. Threshold signature technology (such as ECDSA-TSS) is used to improve security for key management, the improved GHOST protocol is utilized to effectively resist long-range attacks, and well-designed reward and punishment mechanisms are employed to incentivize honest behavior and penalize malicious actions, thus maintaining the security and stability of the entire network.

Cross-layer coordination is key to the efficient functioning of HASC 2.0. Efficient state synchronization between the core layer and the outer layer is achieved through Merkle tree proofs, the security of cross-layer operations is ensured using a joint witness mechanism, and network resources are dynamically allocated based on the load conditions of different layers. This coordination mechanism ensures the consistency and efficient operation of the entire network.

Integration with Layer 2 solutions significantly enables the system to support more complex application scenarios. The core layer is responsible for verifying fraud proofs of Optimistic Rollups, verifying ZK-Rollups' zero-knowledge proofs to ensure the validity of Layer 2 state updates, and serving as the ultimate arbitrator for potential disputes in state channels. This deep integration significantly enhances the scalability and application scope of the entire ecosystem.

Cross-chain interoperability is another important feature of HASC 2.0, allowing Arca Chain to interact seamlessly with other blockchain systems. Core layer nodes participate in the verification and confirmation of cross-chain operations, and the validity of cross-chain asset mapping is determined through TwPoS weight determination. This design provides a solid foundation for building an interconnected blockchain ecosystem and facilitates the flow of assets and data between different networks.
