# Architecture
LitVM is built on a modular, multi-layer architecture that combines the best of Arbitrum's battle-tested rollup technology with BitcoinOS's trustless bridging infrastructure. This design enables LitVM to deliver EVM compatibility, ZK security, and trustless Litecoin integration without requiring any changes to Litecoin's base protocol.
## Architecture Overview
### Core Components
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#### Arbitrum Orbit Rollup
LitVM is built as an **Arbitrum Orbit chain** using the Nitro tech stack. Arbitrum Orbit enables permissionless deployment of customizable chains with:
* **EVM Equivalence** : Full compatibility with Ethereum smart contracts, tooling, and developer experience
* **Fraud Proofs** : Interactive fraud proof mechanism for transaction validity
* **Advanced Compression** : Efficient data batching for lower costs
* **Custom Gas Token** : zkLTC as the native gas token instead of ETH
Why Arbitrum Orbit?
* Battle-tested technology powering billions in TVL
* Active ecosystem of developers and tooling
* Continuous upgrades from Offchain Labs
* Flexibility to customize gas tokens, governance, and more
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#### Succinct zkVM Integration
LitVM enhances the Arbitrum Nitro rollup with **Succinct's SP1 zkVM** to generate validity proofs for all chain execution, creating a **hybrid rollup** architecture:
* **SP1 zkVM** : General-purpose zero-knowledge virtual machine that can prove execution of any Rust program
* **Validity Proofs** : Cryptographic proofs that verify correct state transitions
* **Fast Finality** : Proofs can be verified in minutes rather than the 7-day challenge period of pure optimistic rollups
* **Cost Efficiency** : Proof costs as low as $0.01-0.02 per transaction
This hybrid approach combines:
* The immediate execution speed of optimistic rollups
* The cryptographic security guarantees of ZK rollups
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#### Espresso Shared Sequencer
LitVM utilizes **Espresso's shared sequencer** for decentralized block ordering:
* **Decentralized Sequencing** : Block proposals distributed across a permissionless node network
* **Censorship Resistance** : No single entity controls transaction ordering
* **Cross-Chain Composability** : Shared sequencing enables atomic operations across chains
* **Network Security** : Multiple independent sequencers provide redundancy
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#### Dual Bridge Architecture
LitVM features two bridging systems to connect both the Litecoin and Ethereum ecosystems.
**BitcoinOS Grail Bridge (Litecoin ↔ LitVM)**
The **Grail Bridge** enables trustless LTC movement between Litecoin mainchain and LitVM:
How It Works:
1. **Deposit** : User locks LTC in a Taproot address on Litecoin mainchain
2. **Proof Generation** : BitcoinOS generates a ZK-SNARK proof verifying the locked funds
3. **Minting** : zkLTC is minted on LitVM at 1:1 ratio
4. **Withdrawal** : User burns zkLTC on LitVM, proof is verified, LTC is released on mainchain
Security Model:
* **Non-Custodial** : No third party ever holds user funds
* **1/n Security** : Only one honest validator needed for security
* **ZK Verification** : Proofs are mathematically verifiable—like solving a math problem with a definitive answer
* **No Protocol Changes** : Works with existing Litecoin infrastructure
**Arbitrum Bridge (Ethereum ↔ LitVM)**
As an Arbitrum Orbit chain, LitVM also supports the standard **Arbitrum Bridge** for EVM-native assets:
Supported Assets:
* ETH
* USDC, USDT, and other stablecoins
* ERC-20 tokens
* Other Ethereum-native assets
How It Works:
1. **Deposit** : User deposits assets on Ethereum (or Arbitrum One) via the bridge contract
2. **Confirmation** : After sufficient confirmations, assets are credited on LitVM
3. **Withdrawal** : User initiates withdrawal on LitVM, assets are released after challenge period (or faster with validity proofs)
Benefits:
* Access to Ethereum's deep liquidity
* Familiar bridging experience for EVM users
* Standard security model inherited from Arbitrum
* Gateway for DeFi protocols and stablecoins
**Bridge Comparison**
| **Feature** | **BitcoinOS Grail** | **Arbitrum Bridge** |
| ---------------- | ---------------------- | ---------------------- |
| **Source Chain** | Litecoin | Ethereum / EVM |
| **Asset Type** | LTC → zkLTC | ETH, ERC-20s |
| **Trust Model** | ZK proofs (1/n) | Optimistic + ZK hybrid |
| **Custodian** | None (non-custodial) | Bridge contracts |
| **Primary Use** | Onboard Litecoin users | Onboard Ethereum users |
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## Mainnet Rollout Phases
LitVM's mainnet will be deployed in three phases:
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#### Phase: Ethereum Settlement + Dual Bridges
* Fully operational Arbitrum Orbit rollup settling on Ethereum
* Nitro's optimistic architecture with Succinct zkVM validity proofs
* **BitcoinOS Grail bridge** deployed for trustless LTC bridging
* **Arbitrum Bridge** available for ETH and ERC-20 assets
* Espresso shared sequencer for decentralized block ordering
* zkLTC as gas token and primary base asset
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#### Phase: Litecoin Proof Anchoring
* All finalized chain batches anchored to Litecoin blockchain
* Validity proofs inscribed using standard extended transactions
* No Litecoin protocol changes required
* Creates tamper-resistant audit trail secured by Litecoin's PoW
* Independent verification possible via Litecoin nodes
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#### Phase: Litecoin Native Settlement
* Migration of settlement from Ethereum to Litecoin
* LitVM becomes a fully native Litecoin rollup
* Litecoin as the canonical settlement and finality layer
* Complete sovereignty under Litecoin's 14+ years of PoW security
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## Technical Specifications
| **Component** | **Technology** | **Purpose** |
| ---------------- | ------------------- | --------------------------------------- |
| **Execution** | Arbitrum Nitro | EVM-compatible smart contract execution |
| **Proving** | Succinct SP1 zkVM | Generate validity proofs |
| **Sequencing** | Espresso | Decentralized transaction ordering |
| **LTC Bridging** | BitcoinOS Grail | Trustless LTC ↔ zkLTC transfers |
| **EVM Bridging** | Arbitrum Bridge | ETH, stablecoins, ERC-20 transfers |
| **Gas Token** | zkLTC | Native transaction fee token |
| **Settlement** | Ethereum → Litecoin | State finality and security |
## Network Parameters (Testnet)
| **Parameter** | **Value** |
| ------------------- | ---------------------------------------- |
| **Network Name** | LitVM LiteForge |
| **Chain ID** | 4441 |
| **Native Currency** | zkLTC |
| **RPC URL** | |
| **Block Explorer** | |
| **Block Time** | Variable (on-demand) |
| **Gas Limit** | 32,000,000 (effective) |
| **EVM Version** | Shanghai |
✅ Testnet is live and ready for development.
## Security Considerations
LitVM inherits security from multiple layers:
1. **Litecoin Mainchain** : 14+ years of uninterrupted PoW security
2. **Ethereum Settlement** (Phase 1): World's most decentralized smart contract platform
3. **ZK Proofs** : Mathematical guarantees of execution correctness
4. **Espresso Sequencing** : Decentralized block production prevents censorship
5. **BitcoinOS Grail** : Non-custodial bridging with 1/n security
6. **Arbitrum Bridge** : Battle-tested rollup bridge infrastructure