The TON Adapter is the cross-chain messaging backbone of TAC, enabling secure communication between TON and TAC EVM Layer. Unlike traditional bridges that simply move assets, the TON Adapter is designed specifically for application-level interactions, allowing TON users to execute complex operations on EVM smart contracts seamlessly.
Current Network Status: The sequencer network is currently distributed but not decentralized. Full decentralization is on the roadmap as the network matures.

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Core Purpose

The TON Adapter solves a fundamental challenge in cross-chain interaction: how to securely execute smart contract calls across different blockchain architectures while maintaining user experience that feels native to both sides.
TON Adapter message flow diagram

TON Adapter routing messages between TON and TAC EVM

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Message Structure

Every cross-chain operation begins with a structured message that contains all necessary information for secure execution: 
{
  timestamp: 1640995200,           // TON blockchain timestamp
  target: "0x742d35Cc6473...",     // Target smart contract address
  methodName: "swapTokens(bytes,bytes)", // Method signature
  arguments: "0x1234...",          // Encoded method parameters
  caller: "EQAbc123...",          // Original TON caller address
  mintTokens: [...],              // Tokens to mint on TAC EVM
  unlockTokens: [...]             // Tokens to unlock from previous locks
}
This message structure ensures that sequencers have all the information needed to validate the operation and execute it correctly on the target chain.

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Sequencer Network

The security and reliability of the TON Adapter depends on a distributed network of sequencers that validate and process cross-chain messages.

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Individual Sequencer Operations

Each sequencer in the network operates independently while following the same validation protocols:
  • Event Monitoring: Sequencers continuously monitor both TON and TAC EVM for relevant events. When a user initiates a cross-chain transaction, multiple sequencers detect the event simultaneously.
  • Local Validation: Before participating in consensus, each sequencer validates the transaction locally. This includes verifying asset transfers match message parameters and ensuring the requesting user has sufficient balances.
  • Database Storage: Validated events are stored in each sequencer’s local database, creating a distributed record of all cross-chain activity.
  • Merkle Tree Formation: At regular intervals determined by network parameters, sequencers compile their validated transactions into Merkle trees, creating cryptographic proofs of transaction inclusion.

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Sequencer Groups

The network organizes sequencers into groups to enhance security through redundancy and consensus requirements.

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Network-Wide Consensus

Cross-chain messages only execute after achieving consensus across multiple sequencer groups:
  • Cross-Group Validation: Different groups must submit identical Merkle trees for the same set of transactions. This requirement prevents any single group from manipulating the message flow.
  • Consensus Threshold: The network requires agreement from enough groups to ensure security. The exact threshold is configurable through governance to balance security with efficiency.
  • Execution Triggers: Once sufficient groups agree on a Merkle tree, the transactions within that tree become eligible for execution on the target chain.

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Asset Management

The TON Adapter handles two primary types of asset operations as tokens move between chains.

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Lock and Mint Operations

When assets move from TON to TAC EVM, the TON Adapter employs a lock-and-mint mechanism:
  • Asset Locking: TON native tokens are locked in the TON Adapter contracts on the TON side. This prevents double-spending while maintaining the original asset’s existence.
  • Metadata Capture: The system captures essential token information including name, symbol, decimals, and the original TON contract address.
  • EVM Token Deployment: If this is the first time a particular TON token crosses to TAC EVM, the system automatically deploys a corresponding ERC-20 contract.
  • Token Minting: The equivalent amount of tokens is minted on the TAC EVM side, maintaining supply consistency across both chains.

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Burn and Release Operations

The reverse process handles assets moving from TAC EVM back to TON:
  • Asset Burning: ERC-20 tokens on TAC EVM are burned, removing them from circulation on that side.
  • Validation: Sequencers verify the burn operation and confirm the requesting user’s authorization.
  • Asset Release: The corresponding locked tokens are released back to the user’s TON wallet.

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Epoch-Based Processing

The TON Adapter organizes transaction processing into time-based epochs to ensure orderly and secure message handling.

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Epoch Calculation

Each epoch is calculated using a deterministic formula: 
EpochId = Math.floor((currentTime - protocolDeployTime) / epochDuration);
This creates predictable time windows during which transactions are collected and processed together.

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Processing Windows

Transactions are processed within specific timeframes: 
const epochStart = protocolDeployTime + EpochId * epochDuration;
const epochEnd = protocolDeployTime + (EpochId + 1) * epochDuration;
// Messages processed between epochStart and epochEnd
This time-bounded approach prevents timing attacks and ensures all sequencers are working with the same set of transactions.

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Security Mechanisms

The TON Adapter implements multiple layers of security to protect user funds and prevent malicious activity.

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Message Validation

  • Asset Verification: Sequencers must verify that actual token transfers match the amounts specified in cross-chain messages. This prevents attempts to claim false transfer amounts.
  • Cryptographic Proofs: All transactions include Merkle proofs that allow independent verification of inclusion in the agreed-upon transaction set.
  • Consensus Requirements: Multiple independent groups must agree on transaction validity before execution proceeds.

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Economic Security

  • Collateral Requirements: Sequencer groups must stake significant collateral, creating financial incentives for honest behavior.
  • Slashing Mechanisms: Groups that submit incorrect proofs or behave maliciously face penalties including partial collateral forfeiture.
  • Reward Distribution: Performance-based rewards encourage reliable operation and continued participation in network security.

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Failure Protection

When cross-chain transactions fail, the TON Adapter automatically protects user assets through rollback mechanisms.
  • Automatic Rollbacks: If a transaction fails on the target chain, assets are automatically returned to the sender rather than being lost.
  • Failed Transaction Collection: Failed transactions are collected into special Merkle trees and processed through the same consensus mechanism to ensure proper resolution.
  • Timeout Protection: Transactions that don’t complete within specified time windows are automatically rolled back to prevent funds from being permanently locked.

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Smart Contract Integration

The TON Adapter interfaces with smart contracts on both chains through standardized protocols.

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CrossChainLayer Contract

On TAC EVM, the CrossChainLayer contract serves as the main interface: 
interface ICrossChainLayer {
    function receiveMessage(
        bytes32 messageHash,
        bytes calldata merkleProof,
        MessageData calldata message
    ) external;

    function sendMessage(
        OutMessageV1 calldata outMessage
    ) external;
}
This contract validates Merkle proofs, manages asset operations, and routes messages to target applications.

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Message Execution Process

When executing cross-chain messages:
  • Proof Validation: The CrossChainLayer contract verifies that the message is included in a consensus-approved Merkle tree.
  • Asset Operations: Any required token minting or unlocking operations are performed before calling the target contract.
  • Contract Invocation: The target smart contract method is called with the decoded parameters from the cross-chain message.
  • Result Handling: Any return values or additional cross-chain messages are processed through the same secure routing system.

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Performance Characteristics

The TON Adapter is designed to balance security with reasonable performance for application-level interactions.
Cross-chain transactions typically complete within minutes rather than hours. The exact timing depends on epoch duration settings and the number of sequencer groups participating in consensus.This latency is acceptable for most application use cases.

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What’s Next?

Understanding the TON Adapter’s role in message routing helps you build more effective hybrid dApps and proxy contracts.

Proxy Apps

Learn how smart contracts interface with the TON Adapter

Cross-Chain Messaging

Dive deeper into message structure and validation