Architecture

Overview

Protocol v2 introduces TSS (Threshold Signature Scheme) based cross-chain infrastructure, enabling secure asset transfers across heterogeneous chains including Bitcoin. This document describes the overall architecture and component interactions.

System 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 │               │    │                                │
│  └─────────────┘               │    │                                │
└────────────────────────────────┘    └────────────────────────────────┘

Component Details

On-Chain Components (MAP Relay Chain)

Maintainer Manager

Manages the lifecycle of Maintainers:

• Registration: Validators can register as Maintainers

• Election: Periodic election of active Maintainer set

• Incentives: Distribution of cross-chain fee rewards

• Slashing: Penalty for malicious or offline behavior

TSS Manager

Manages TSS key generation and switching:

• KeyGen Coordination: Triggers and monitors KeyGen process

• Vault Registration: Records new Vault addresses

• Churn Process: Coordinates TSS switching during Maintainer set changes

Vault Manager

Manages Vault state across all chains:

• State Tracking: Active, Retiring, Retired states

• Asset Recording: Tracks assets in each Vault

• Migration: Coordinates asset migration during Churn

Relay

Manages cross-chain transaction flow:

• TxIn Processing: Records inbound cross-chain transactions

• TxOut Scheduling: Queues outbound transactions for signing

• Status Tracking: Monitors transaction completion

Registry

Central registry for protocol configuration:

• Chain Registry: Supported chains and their parameters

• Token Registry: Supported tokens and mappings

• Alias Registry: Human-readable names for addresses

Gas Service

Manages cross-chain gas fees:

• Fee Calculation: Determines fees for each chain

• Fee Updates: Allows dynamic fee adjustment

• Fee Collection: Records collected fees

On-Chain Components (Other Chains)

Gateway

Entry/exit point for cross-chain operations:

• Deposit Handling: Receives user deposits

• Signature Verification: Verifies TSS signatures

• Withdrawal Execution: Releases assets on valid signature

• TSS Key Update: Updates TSS public key during Churn

Vault Address

TSS-controlled address for asset custody:

• Multi-chain: Same TSS key generates addresses for all chains

• No Private Key: No single entity holds the private key

• Threshold Control: Requires 2/3 Maintainers to sign

Off-Chain Components (Maintainer Node)

Observer

Monitors cross-chain events:

• Event Detection: Watches for deposits, withdrawals

• Data Parsing: Extracts cross-chain parameters

• Submission: Reports observations to MAP Relay Chain

Signer

Participates in TSS operations:

• KeyGen: Generates key share during TSS setup

• KeySign: Participates in transaction signing

• Key Storage: Securely stores local key share

P2P Network

Communication layer between Maintainers:

• Discovery: Finds other Maintainer nodes

• Messaging: Exchanges TSS protocol messages

• Consensus: Coordinates signing sessions

Data Flow

Inbound Transaction (TxIn)

1. User deposits to Vault on Source Chain
2. Observers detect deposit event
3. Observers submit observation to MAP Relay Chain
4. When 2/3+ observations match, TxIn is confirmed
5. Relay contract records the inbound transaction
6. User's balance is credited on target representation

Outbound Transaction (TxOut)

1. User requests withdrawal on MAP Relay Chain
2. Relay contract creates TxOut record
3. Maintainers receive signing request
4. TSS KeySign produces signature
5. For contract chains: signature submitted to Gateway
6. For Bitcoin: signed transaction broadcast to network
7. Assets released from Vault to user

Security Architecture

Threshold Security

• 2/3 Threshold: Requires 2/3 of Maintainers for any operation

• No Single Point of Failure: No individual can control assets

• Byzantine Fault Tolerance: System continues with up to 1/3 malicious nodes

Slashing Conditions

Violation	Penalty
Double signing	Severe slash + jail
Offline during KeySign	Slash points accumulation
Invalid observation	Slash points
Failure to participate in KeyGen	Jail

Key Rotation (Churn)

Regular key rotation ensures:

• Removal of compromised Maintainers

• Addition of new Maintainers

• Fresh key material

Integration with Light Client

Protocol v2 can optionally integrate light client verification:

┌─────────────────────────────────────────────────────────────────┐
│                     Enhanced Verification                        │
│                                                                  │
│  1. TSS signature provides fast finality                        │
│  2. Light client provides additional cryptographic proof        │
│  3. Either can be used independently or combined                │
│                                                                  │
└─────────────────────────────────────────────────────────────────┘

This hybrid approach offers:

• Speed: TSS signature for fast confirmation

• Security: Light client for trustless verification

• Flexibility: Choose based on use case requirements