# Overview ## Design Goals and Background MAP Protocol v2.0 is a decentralized cross-chain protocol based on TSS (Threshold Signature Scheme). The protocol enables secure cross-chain asset transfers through threshold signature technology without relying on traditional multi-sig wallets or centralized custody solutions. **Core Design Goals:** * **Decentralized Security**: Through TSS threshold signatures, no single node can independently control cross-chain assets * **High Fault Tolerance**: The system can tolerate up to 1/3 of nodes failing or acting maliciously * **Multi-chain Support**: Supports EVM-compatible chains, Bitcoin, and other heterogeneous chains * **On-chain Governance**: Maintainer management and state consensus implemented through Solidity contracts on MAP Relay Chain ## System Roles ### Validator * Block producers and consensus participants of MAP Relay Chain * Responsible for validating and confirming cross-chain transactions * Participate in network consensus by staking MAPO tokens * Validators can register as Maintainers to participate in cross-chain signing ### Maintainer * Core participants in cross-chain signing * Elected from registered Validators * Responsibilities: * Monitor cross-chain events on source chains (Observer) * Participate in TSS key generation (KeyGen) * Participate in cross-chain transaction signing (KeySign) * Submit observation results to MAP Relay Chain * Hold TSS private key shares, collectively managing Vault addresses ### Relayer * Responsible for submitting signed transactions to target chains * Receive transaction fee subsidies and rewards * Can be Maintainer nodes or independent service providers * For contract chains, anyone can submit signatures to the target chain Gateway ### LP Provider (Liquidity Provider) * Provide liquidity to cross-chain pools * Receive cross-chain fee sharing and LP incentives * Participate by depositing assets to Vault addresses ## Overall Architecture ``` ┌─────────────────────────────────────────────────────────────────────────────┐ │ User/DApp │ └─────────────────────────────────────────────────────────────────────────────┘ │ ▼ ┌─────────────────────────────────────────────────────────────────────────────┐ │ Source Chain │ │ ┌─────────────┐ ┌─────────────┐ ┌─────────────┐ │ │ │ Gateway │ │ Vault │ │ Cross-chain │ │ │ │ Contract │───▶│ Address │───▶│ Events │ │ │ └─────────────┘ └─────────────┘ └─────────────┘ │ └─────────────────────────────────────────────────────────────────────────────┘ │ │ Observer Monitoring ▼ ┌─────────────────────────────────────────────────────────────────────────────┐ │ Maintainer Network │ │ ┌─────────────┐ ┌─────────────┐ ┌─────────────┐ ┌─────────────┐ │ │ │ Maintainer │ │ Maintainer │ │ Maintainer │ │ Maintainer │ │ │ │ A │◀──▶│ B │◀──▶│ C │◀──▶│ D │ │ │ └─────────────┘ └─────────────┘ └─────────────┘ └─────────────┘ │ │ │ │ │ │ │ │ └──────────────────┴──────────────────┴──────────────────┘ │ │ │ │ │ P2P Network Communication │ │ TSS KeyGen / KeySign │ └─────────────────────────────────────────────────────────────────────────────┘ │ │ Submit Observations/Votes ▼ ┌─────────────────────────────────────────────────────────────────────────────┐ │ MAP Relay Chain │ │ │ │ ┌──────────────────┐ ┌──────────────────┐ ┌──────────────────┐ │ │ │ Maintainer │ │ TSS │ │ Relay │ │ │ │ Manager │ │ Manager │ │ │ │ │ │ Register/Elect/ │ │ TSS Generation/ │ │ Cross-chain │ │ │ │ Incentive/Slash │ │ Switching │ │ Flow Management │ │ │ └──────────────────┘ └──────────────────┘ └──────────────────┘ │ │ │ │ ┌──────────────────┐ ┌──────────────────┐ ┌──────────────────┐ │ │ │ Vault │ │ Registry │ │ Gas │ │ │ │ Manager │ │ │ │ Service │ │ │ │ State Transition/│ │ Chain/Token/ │ │ Fee Recording/ │ │ │ │ Asset Recording │ │ Alias Registry │ │ Updating │ │ │ └──────────────────┘ └──────────────────┘ └──────────────────┘ │ │ │ └─────────────────────────────────────────────────────────────────────────────┘ │ ┌──────────────────┴──────────────────┐ │ │ ▼ ▼ ┌────────────────────────────────┐ ┌────────────────────────────────┐ │ Contract Chains (EVM/Solana) │ │ Non-contract Chains (Bitcoin) │ │ │ │ │ │ TSS signature submitted to │ │ TSS builds and signs tx │ │ Relay Chain │ │ │ │ │ │ │ │ ▼ │ │ ▼ │ │ Broadcast to target chain │ │ Relayer/Anyone submits sig │ │ │ │ │ │ │ │ ▼ │ │ ▼ │ │ ┌─────────────┐ │ │ ┌─────────────┐ │ │ │ Vault │ │ │ │ Gateway │ │ │ │ Address │ │ │ │ Verify sig │ │ │ │ (TSS) │ │ │ │ Execute │ │ │ └─────────────┘ │ │ │ TSS Switch │ │ │ │ │ └─────────────┘ │ │ │ └────────────────────────────────┘ └────────────────────────────────┘ ``` ## Core Components ### On-chain Components **MAP Relay Chain Contracts:** | Component | Function | | ------------------ | ------------------------------------------------------------------ | | Maintainer Manager | Maintainer registration, updates, election, and incentive/slashing | | TSS Manager | Manage TSS generation and switching processes | | Relay | Manage cross-chain flow on Relay Chain | | Vault Manager | Vault state transitions and asset recording per chain | | Registry | Register and manage supported chains, tokens, and aliases | | Gas Service | Record and update fee information for each chain | **Other Chain Contracts:** | Component | Function | | --------- | ------------------------------------------------------------------------------ | | Gateway | Receive/send cross-chain assets, verify TSS signatures, complete TSS switching | ### Off-chain Components (Maintainer Nodes) | Component | Function | | ------------- | ----------------------------------------------------------------------------- | | Observer | Monitor cross-chain events on each chain, parse and submit to MAP Relay Chain | | Signer | Participate in TSS KeyGen and KeySign processes | | P2P Network | Communication network between Maintainer nodes | | Local Storage | Local storage for key shares, pending transactions, etc. | ## Vault State Model Vault is an address managed by TSS, used to custody cross-chain assets. Each Vault has the following states: ``` ┌──────────┐ Election Complete ┌──────────┐ New Vault Activated ┌──────────┐ │ Pending │ ─────────────────────▶ │ Active │ ─────────────────────▶ │ Retiring │ │ │ │ │ │ │ └──────────┘ └──────────┘ └──────────┘ │ │ Asset Migration Complete ▼ ┌──────────┐ │ Retired │ │ │ └──────────┘ ``` | State | Description | | -------- | ---------------------------------------------------------------------------------------------- | | Active | Currently active Vault, receives new cross-chain deposits | | Retiring | Vault being migrated, no longer receives new deposits, waiting for asset migration to complete | | Retired | Vault with completed asset migration, no longer in use | **Notes:** * If users mistakenly transfer assets to a Retired Vault and the corresponding TSS nodes are still running, the system will automatically refund the assets to the user * The system synchronizes all Vaults in Active and Retiring states * Also synchronizes Retired Vaults generated within a certain number of recent blocks (for handling delayed transaction confirmations and refunds) ## TSS Threshold Signature MAP Protocol v2.0 uses TSS (Threshold Signature Scheme) for decentralized asset custody. **Basic Principles:** * Private keys are split into multiple shares distributed across different Maintainer nodes * Signing requires at least 2/3 of nodes to collaborate * No single node can independently generate a valid signature **Key Processes:** | Process | Description | | ------- | ------------------------------------------------------------------------------------------------- | | KeyGen | Key generation, after election, new Maintainer set collaboratively generates new Vault public key | | KeySign | Transaction signing, Vault Maintainer members collaborate to generate transaction signature | **Supported Signature Algorithms:** | Algorithm | Use Cases | | --------- | --------------------------------------------------------------------- | | secp256k1 | Bitcoin, EVM-compatible chains, and other chains supporting secp256k1 | **Handling Chains Not Natively Supporting secp256k1:** * For chains like Solana using ed25519, verification is completed by verifying secp256k1 signatures through on-chain contracts * Gateway contracts are responsible for verifying TSS signature validity ## Glossary | Term | Description | | ----------- | ----------------------------------------------------- | | TSS | Threshold Signature Scheme | | Maintainer | Core participant in cross-chain signing | | Validator | Validator of MAP Relay Chain | | Vault | Cross-chain asset custody address managed by TSS | | KeyGen | TSS key generation process | | KeySign | TSS transaction signing process | | Churn | TSS switching/rotation process | | Observer | Module that monitors cross-chain events on each chain | | Gateway | Cross-chain contract on other chains | | Epoch | Period of MAP Relay Chain | | Slash Point | Penalty points | | Jail Epoch | Imprisonment period count | | TxIn | Inbound transaction (Source Chain → Relay Chain) | | TxOut | Outbound transaction (Relay Chain → Target Chain) | | Memo | Cross-chain information field for non-contract chains |