🌐 Overview

• The Hemi Network represents a different way of thinking about Layer-2 scaling, by approaching Bitcoin and Ethereum as components of a supernetwork.

• This modular protocol aims to scale these networks and maximize their utility, creating a more connected and efficient blockchain ecosystem.

• Through features such as the hVM, Hemi equips developers with robust tools for building next-generation dApps with Bitcoin and Ethereum interoperability.

💡 The Benefits of Hemi

🌐 Overview

• In contrast to other Layer 2 (L2) rollup solutions, the Hemi Network introduces a more decentralized approach to data publication and validation, addressing critical issues present in current L2 setups:

  • ✅ Decentralized Roles: Introduces a decentralized approach with Publishers handling key roles asynchronously, mitigating the risks associated with centralized control found in other L2 networks.

  • ✅ Incentivized Participation: Allows open participation through staking tokens with Ethereum-side validation contracts, fostering consistent and incentivized data sharing even during times of increased fee activity.

  • ✅ Fault Tolerance and Reward System: Implements a system to discourage malicious behavior, slashing stakes of Publishers submitting invalid data while rewarding Challengers who identify faults, thereby promoting network integrity.

  • ✅ Efficient Ethereum Fee Management: Manages rewards via Ethereum-side validation contracts, ensuring consistent incentives for Publishers despite Ethereum fee fluctuations.

🔒 Network Security and Finality

• To inherit Bitcoin security, a new type of miner (a “PoP Miner”) publishes Hemi consensus information to the Bitcoin blockchain.

• After a state publication to Bitcoin, the Hemi Network’s consensus layer incorporates cryptographic proofs of these publications, with PoP Miners receiving a reward in the protocol’s native token. The network uses these proofs during fork resolution to prevent reorganizations with the full force of Bitcoin’s security.

• As they are produced, the Hemi Network’s chain segments initially receive Bitcoin confirmations, which means an attacker would have to control increasingly large ratios of staking power to successfully affect a reorganization.

• During normal operation, each block on the Hemi Network reaches full “Bitcoin Finality” after 90 minutes, or nine Bitcoin blocks, on average.

At this point, it is mathematically impossible for anyone to reorganize the network without 51% attacking Bitcoin itself.

🌐 Overview

• Ethereum Rollups are a Layer-2 scaling solution designed to enhance the throughput and features of the Ethereum network.

• They operate by "rolling up," or bundling, multiple transactions off-chain and submitting them in batches to the Ethereum mainnet for data availability. By doing so, they significantly reduce congestion and gas fees while maintaining interoperability with Ethereum.

• Rollups can also add new protocol features that would be impossible directly on Ethereum (e.g., PoP security to inherit Bitcoin Finality and Hemi's hVM Bitcoin Interoperability system).

🌐 Overview

• The Hemi Network connects to both the Bitcoin and Ethereum networks, allowing asset portability across both, enabling a third-party cross-chain ecosystem. To create this highly secure multichain ecosystem, the Hemi Network operates several kinds of decentralized nodes: Bitcoin finality governors, Bitcoin-secure sequencers, Proof-of-Proof miners, and a modified Geth node.

🛡️ Bitcoin Finality Governors (BFGs)

• Regulate the network's security status by analyzing Bitcoin blocks for Hemi Network state proofs.

• Determine the network's finality status, ensuring security.

• Coordinate with Bitcoin-secure sequencers and proof-of-proof miners.

⚙️ Bitcoin-Secure Sequencers (BSS Nodes)

• Integrate Hemi Network transactions with Ethereum mainnet transactions.

• Maintain the network's consensus layer and manage staking, unstaking, and slashing operations.

• Ensure a seamless connection between the Hemi Network and Ethereum for asset transfers.

🛠️Modified Geth Node

• Operates as a customized Ethereum node, providing compatibility and connectivity between the Hemi Network and Ethereum.

• Ensures data synchronization and transaction processing within the Hemi Network ecosystem.

🔗 Proof-of-Proof Miners (PoP Miners)

• Secure the network by embedding state proofs into the Bitcoin blockchain.

• Hash network headers to create cryptographic proofs and publish these to Bitcoin.

• Receive tokens as rewards for their contributions.

⚡️ Achieving Decentralized Interoperability

This innovative approach ensures secure, decentralized interoperability among Bitcoin, Ethereum, the Hemi Network, and other EVM-compatible chains.

🌐 Welcome to the Hemi Developer Quickstart Guide!

This guide provides an overview of the essential steps and resources to get you started with building on Hemi. Whether you’re new to blockchain development or an experienced web3 developer, this guide will help you navigate Hemi’s ecosystem and leverage its full potential.

1️⃣ Explore the Hemi Network

Begin by familiarizing yourself with the Hemi network’s architecture, key features, and its unique approach to interoperability and scalability.

2️⃣ Set Up Your Development Environment

Prepare your development environment to start building on Hemi by setting up the necessary tools and configurations. This step ensures you have everything in place to interact with the Hemi network effectively.

3️⃣ Interact with Hemi Apps

Dive into the Hemi ecosystem by exploring and interacting with decentralized applications (dApps) built on the network. This hands-on approach helps you understand Hemi’s functionality and how dApps operate within the blockchain environment.

4️⃣ Build on Hemi!

Start developing your own decentralized applications (dApps) on Hemi using its powerful suite of developer tools and resources. This section will guide you through the process of creating, testing, and deploying your projects on the Hemi network.

❓ What Now?

Congratulations on getting started with Hemi! 🎉

Now that you’ve set up your environment, explored various apps, and begun building on the network, here are the next steps to deepen your engagement and maximize the potential of your development journey on Hemi.

📐Troubleshooting

If you encounter any issues or need assistance at any step, the following resources are available to help:

🌐 Overview

Welcome to the technical documentation for Hemi, a Layer-2 solution for Bitcoin and Ethereum blockchains that offers true scalability and interoperability.

✈️ Navigating the Docs

Our documentation is organized into the following sections to help you find relevant information quickly:

⚡ Quickstart: Whether you plan to develop, explore, or mine on Hemi, we have identified some crucial resources to quickstart your journey.

⚡ Foundational Topics: Learn about the architecture, sequencer consensus, PoP consensus & Bitcoin finality, tunneling, and more.

⚡ How-To Tutorials: Whether you are using or developing on Hemi, these basics will get you started! Set up your MetaMask Wallet, tunnel ETH and BTC to Hemi, start with Remix IDE, deploy an ERC-20 token and run a PoP miner.

⚡ Tooling: Understand and access the tools required to build on Hemi.

⚡Incentives: Check out our points, grants, retroactive funding, and one-off spends.

⚡ Additional Resources: Partners inquiry, FAQ, official links, and our brand kit.

⚡ Send Feedback: We'd love to hear from you, good or bad! Found a bug? Got a hackathon coming up? Slide into our DMs.

🏁 Getting Started

Whether you're a developer, miner, or explorer, we've got a path for you!

👇 Select Your Role

Hemi Mainnet

Additional Mainnet Public RPC Endpoints

• BFG (for PoP Mining): wss://rpc.hemi.network/v1/ws/public

Code Snippets

Example HTTP request:

Hemi Testnet

Additional Testnet Public RPC Endpoints

• BFG (for PoP Miner): wss://testnet.rpc.hemi.network/v1/ws/public

Code Snippets

Example HTTP request:

🌐 Welcome to the Hemi Developer Quickstart Guide!

This guide provides an overview of the essential steps and resources to get you started navigating Hemi’s ecosystem and leveraging its full potential.

1️⃣ Explore the Hemi Network

Begin by familiarizing yourself with the Hemi network’s architecture, key features, and its unique approach to interoperability and scalability.

2️⃣ Set Up Your Wallets

Prepare your various wallets to start exploring Hemi by setting up an EVM and BTC wallet. This step ensures you have everything in place to interact with the Hemi network effectively.

3️⃣ Interact with Hemi Apps

Dive into the Hemi ecosystem by exploring and interacting with decentralized applications (dApps) built on the network. This hands-on approach helps you understand Hemi’s functionality and how dApps operate within the blockchain environment.

❓ What Now?

Congratulations on getting started with Hemi! 🎉

Now that you’ve set up your environment, explored various apps, and begun building on the network, here are the next steps to deepen your engagement and maximize the potential of your journey on Hemi.

📐Troubleshooting

If you encounter any issues or need assistance at any step, the following resources are available to help:

🌀 Conventional Rollups

💭 Things to Consider

Centralized Influence in a Decentralized Sequencing World

Within frameworks aiming for decentralized sequencing, the presence of a centralized proposer could wield significant influence, potentially disrupting their intended decentralized nature.

Such control might result in the withholding of valid state rollups from Ethereum, leading to coercion of decentralized sequencers into potential censorship or halting communication of specific chain segments back to Ethereum for settlement.

🟩 Verifiers and Challenges

Vulnerabilities in optimistic rollup networks pose risks of asset theft through forged L2 states. To address this, rollups introduce verifiers, but the lack of proper incentives for this role presents challenges.

These lack of incentives can lead to difficulties such as:

• 🔒 Securing a sufficient number of verifiers to perform the complex and expensive verification process required.

• 👥 Relying heavily on users or nodes funded by development teams resulting in centralization.

• 📣 Potential bias or influence.

• 🌎 Sustainability and scalability issues.

✋ Denial-of-Service Risks

L2 networks' reliance on centralized "batchers" can expose them to denial-of-service risks if batchers refuse to publish transactions back to Ethereum for data availability.

🛡️ Inherits Bitcoin's Security

• Hemi's network capitalizes on Bitcoin's formidable security through a mechanism known as Proof-of-Proof (PoP). This approach allows Hemi to inherit the solid Proof-of-Work (PoW) security of Bitcoin.

🔍 How?

• To achieve this, Hemi deploys specialized miners, referred to as PoP Miners. These miners are responsible for:

  • Gathering crucial network details and publishing them on Bitcoin's blockchain, thereby linking Hemi's security directly to Bitcoin's proven system.

  • Employing sophisticated algorithms to generate proofs that are vital for the network's security.

  • Ensuring Hemi's network integrity by leveraging Bitcoin's security, providing a dual layer of protection.

• This integration with the Bitcoin blockchain affords Hemi an additional security layer, utilizing Bitcoin's PoW system as a basis for resolving disputes and ensuring trustworthiness.

🏗️ Block Confirmations

• New segments in the Hemi chain receive confirmations from Bitcoin, significantly raising the barrier for potential attacks. These confirmations:

  • Serve as "security bricks," each one strengthening the network's defenses.

  • Ensure that any attempt to compromise the network requires substantial power, making unnoticed attacks virtually impossible.

  • As Bitcoin confirmations accumulate, the Hemi Network's "security wall" becomes increasingly formidable, creating an effective deterrent against malicious actors.

🔚 Conclusion

• The Proof-of-Proof (PoP) consensus mechanism uniquely positions the Hemi Network by:

  • Allowing Bitcoin miners to secure Hemi indirectly, without direct involvement in Hemi's consensus processes.

  • Facilitating scalable transaction throughput in the Hemi ecosystem without expanding its Bitcoin footprint significantly.

  • Setting a high barrier for network reorganizations, as disrupting Hemi would necessitate a highly improbable 51% attack on Bitcoin itself, a task too daunting even for nation-states.

• This approach not only extends Bitcoin's security to the Hemi Network but also introduces a scalable, robust framework for transaction processing and network integrity.

⛔️ The Trouble With Merged Mining

• Bitcoin miners must choose to participate by running nodes for the sidechain, which can curtail decentralization.

• This makes the sidechain more susceptible to attack, as Bitcoin miners can collude to attack the sidechain at no cost while reaping Bitcoin block rewards.

• Merged mining can introduce new security problems and issues with incentives.

🔍 How Proof-of-Proof Works

• Hemi uses a consensus protocol called Proof-of-Proof (PoP), which allows Hemi to exceed Bitcoin's security at scale.

• Bitcoin miners don’t need to participate in Hemi directly; they confirm blocks that include Hemi transactions and collect transaction fees for doing so.

• Users who do want to earn rewards in Hemi’s native token can run a super-lightweight PoP miner to publish Hemi consensus data to Bitcoin.

• Each new Hemi block receives a Bitcoin confirmation, making reorganization increasingly unlikely until the block reaches finality.

Thus, in the Proof-of-Proof protocol, unlike with merged mining, Bitcoin miners needn’t be active to benefit; they can’t collude to attack the chain, and superfinality comes fast.

🚨 Weak Subjectivity

• This risk involves an attacker accumulating enough keys of old PoS miners to gain majority control at some point in the past. With this control, they could create a valid, alternative/competing version of the blockchain which would appear equally valid to a bootstrapping node attempting to sync the network for the first time, and could also be used to create seemingly valid zero-knowledge proofs of chain state that differs from the legitimate canonical chain.

• While Ethereum relies on community consensus to avoid long-range reorganizations of its chain, its PoS protocol doesn’t technically prevent this type of attack.

🚫 Censorship

• An attacker with current majority stake could potentially block or ignore certain transactions, exercising a form of majority control that undermines the network's decentralization and fairness.

❌ Lack of Protocol-Level Defenses

• Since PoS operates entirely within its network, it lacks protocol-level defenses against the types of attacks mentioned above.

• Among the vulnerabilities, the limitations are:

  • No External Correction Mechanism: If internal rules fail or are exploited, there's no external system to protect or correct the network.

  • Self-Contained Security: PoS systems handle all their security internally within the blockchain network.

• By using PoP, Hemi prevents against weak subjectivity attacks because the illegitimate chain an attacker produces when attempting a long-range reorg could not be appropriately published to Bitcoin. Hemi's fork resolution algorithm prevents a reorg from occurring if the new proposed fork does not have PoP publications that are in-step with or before the current chain's publications. As a result, Hemi's consensus algorithm has strong subjectivity and reorganizing a segment of Hemi's chain which has reached Bitcoin finality would require the attacker to 51% attack Hemi and Bitcoin simultaneously.

• As a dual-chain L2, Hemi can also provide robust censorship resistance against attacks from majority block-consensus power actors. Any valid Hemi transaction can be published to either Bitcoin or Ethereum, and Hemi's block derivation protocol will force the inclusion of these transactions in Hemi blocks.

🌐 Overview

• Blockchain networks typically operate as independent systems with no knowledge of other networks, creating a siloed environment. This isolation makes it impossible to transfer assets directly from one chain to another.

• Bridges are developed to address this issue, enabling asset transfers between different blockchains. They function by accepting a token from one blockchain (chain A) and issuing a corresponding placeholder or wrapped token on another blockchain (chain B). This wrapped token represents the original token and can be redeemed for it.

🖼️ Example

• To illustrate, consider the process of transferring bitcoin to Ethereum. A user sends bitcoin to a bridge connecting to the Ethereum network. This bridge then issues a wrapped Ethereum token representing the bitcoin.

• The user can utilize this wrapped bitcoin within the Ethereum network or return it to the bridge to reclaim the original bitcoin on the Bitcoin network.

🔍 Broader Applications & Limitations of Bridges

• Bridges are not limited to transferring assets between distinct blockchains. They can also facilitate transfers between different network layers, like connecting a Layer 1 (L1) blockchain like Ethereum to a Layer 2 (L2) rollup chain. This connection allows assets to benefit from the L2's lower fees and other features.

• However, bridges often rely on centralized infrastructure due to the lack of protocol-level awareness between the connected chains. For example, while an L2 might maintain the state of its corresponding L1, the L1 lacks inherent knowledge of the L2. This disconnect necessitates a centralized third party to maintain awareness of both chains.

🔒 Security and Efficiency

• The security model behind Hemi’s Ethereum Tunnels leverages the strengths of both Ethereum and Bitcoin. By integrating Bitcoin finality, Hemi ensures that cross-chain transactions achieve a level of finality backed by Bitcoin’s Proof-of-Work consensus, widely considered the most secure consensus mechanism in blockchain technology.

• This significantly reduces the time it takes to finalize cross-chain transactions and provides strong protection against censorship or fraud attempts during the tunneling process.

• The decentralized Challenger role also strengthens Hemi’s security. Rather than relying on a centralized entity to raise disputes, any participant in the Hemi ecosystem can act as a Challenger, further decentralizing the network and increasing its resistance to fraud.

• This approach contrasts with centralized bridges, which can be vulnerable to manipulation or collusion by a single entity overseeing the dispute process.

🏗️ A Phased Approach

The phased approach to Hemi’s Ethereum and Bitcoin Tunnels aims to progressively enhance the security, decentralization, and asset support for cross-chain transfers. Each phase introduces key improvements to the settlement mechanisms and expands the range of assets that can be tunneled across Ethereum, Bitcoin, and Hemi, all while focusing on increasing trust minimization and reducing reliance on centralized actors.

🚊 How Ethereum Tunnels Work

The Ethereum Tunnel process involves locking assets on one network while minting corresponding representative tokens on the other network. For Ethereum-native assets, tokens are minted on Hemi once the assets are locked in a Hemi validation contract on Ethereum.

This allows seamless asset transfers across chains, enabling users to leverage the strengths of both networks while minimizing the friction of cross-chain operations.

Deposit to Hemi

1. The process begins with the user initiating a deposit transaction on Ethereum. This deposit locks up Ethereum-native tokens in a Hemi validation contract on Ethereum. The validation contract plays a critical role by securing the assets and ensuring they remain locked throughout the tunneling process.

2. Once the deposit is secured in an Ethereum block, Hemi’s block derivation protocol kicks in. The Sequencer, responsible for ordering and generating Hemi blocks, is required to include the deposit in the first Hemi block derived from the Ethereum block that contains the deposit transaction. This ensures that the deposit is acknowledged in Hemi’s L2 environment almost immediately after its validation on Ethereum.

3. After the deposit is included, Hemi mints a representative token on the Hemi Network, which serves as the equivalent of the locked asset on Ethereum. This token can now be freely used within the Hemi ecosystem, allowing users to engage with dApps or perform any transaction that requires the asset. You should receive your deposit within 0-2 minutes.

Withdrawal to Ethereum

1. To return the assets back to Ethereum, the user submits a withdrawal transaction on Hemi. When the withdrawal request is submitted, the representative tokens on Hemi are burned, which signals the user’s intent to withdraw their corresponding Ethereum-native assets.

2. Hemi’s state transition system updates its rollup state root, which is then submitted to Ethereum by a Publisher. The state root acts as a cryptographic proof of the transactions that occurred on Hemi, including the user’s withdrawal request.

3. The key to finalizing the withdrawal lies in Hemi’s use of Bitcoin finality, which is a significant differentiator from other optimistic rollup bridges. (In traditional optimistic rollups, the finality of cross-chain transactions is delayed by a dispute window, during which fraud proofs can be raised. Hemi accelerates this process by leveraging Bitcoin’s highly secure Proof-of-Work consensus mechanism to finalize the state root on Ethereum.) This process takes roughly 40 minutes.

4. Once Bitcoin finality is achieved, and assuming no disputes are raised through the decentralized Challenger role, the state root is confirmed, and the user can submit a withdrawal proof on Ethereum to claim their assets from the Hemi validation contract. A proof may take up to 24 hours.

5. The withdrawal proof ensures that the burned representative tokens on Hemi correspond to the original locked Ethereum-native tokens. Upon successful validation of the proof, the Ethereum-native assets are unlocked, completing the cross-chain asset transfer.

🔄 Tunneling Hemi-Native and Bitcoin-Native Assets to Ethereum

Hemi’s tunneling process is not limited to Ethereum-native assets. Phase 2 of Hemi's Ethereum Tunnel will support Hemi-native and Bitcoin-native assets, extending the functionality of the tunnels to a broader range of assets. This capability is crucial for enabling the use of Bitcoin within Ethereum’s extensive decentralized finance (DeFi) ecosystem, which traditionally lacks native Bitcoin interoperability.

Withdrawal to Ethereum

1. The process for tunneling Hemi-native assets begins with the user submitting a deposit transaction on Hemi, locking their native assets within Hemi’s native asset tunnel contract.

2. Similar to Ethereum-native asset transfers, the state root containing this deposit transaction is published to Ethereum.

3. Once the rollup state root is confirmed (following Bitcoin finality and the absence of any disputes), the user submits a deposit proof on Ethereum to claim the corresponding representative tokens. These tokens represent the Hemi-native assets within the Ethereum ecosystem and can be used in Ethereum dApps or traded just like any other Ethereum-based token.

Deposit to Hemi

1. Moving Hemi-native assets back to Hemi from Ethereum involves a similar process. The user initiates a withdrawal on Ethereum, burning the representative tokens.

2. This triggers Hemi’s block derivation protocol to include the withdrawal in the next Hemi block derived from the corresponding Ethereum block.

3. Once the withdrawal is processed, the Hemi-native assets are transferred from Hemi’s native asset tunnel contract back to the user, completing the return to Hemi’s L2 environment.

One of the core advantages of this system is its flexibility. It allows Bitcoin-native assets, which are traditionally siloed on the Bitcoin network, to be tunneled through Hemi and into Ethereum. This enables Bitcoin to participate in Ethereum’s DeFi ecosystem while maintaining the security and decentralization that Bitcoin’s Proof-of-Work consensus provides.

🔍 Comparison to Standard Ethereum Bridges

While Hemi’s Ethereum Tunnels share the foundational principles of traditional bridges like the Standard Bridge, there are several critical distinctions:

• The primary distinction between Hemi’s Tunnels and standard bridges lies in the finality model and security architecture. Standard bridges depend on an optimistic model with a delayed dispute window. The withdrawal process on these bridges typically takes a week or longer, as they await the potential for fraud proofs before finalizing the transaction.

• Hemi Tunnels enhance this process by incorporating Bitcoin finality. Instead of relying solely on an Ethereum-based dispute window, Hemi uses Bitcoin’s Proof-of-Work consensus as an additional layer of security. This allows Hemi to finalize transactions more quickly, as the Bitcoin network’s finality period is shorter and more secure than the traditional dispute windows of optimistic rollups.

• Hemi will decentralize the dispute process by distributing the Challenger role across a wider set of participants. This decentralization mitigates the risk of collusion or centralization of power within the bridging system, offering a more secure alternative to centralized or semi-centralized dispute mechanisms found in standard bridges.

🌐 Overview

• A block is a component of blockchain technology that contains transactions and their associated data.

• Its security is enhanced because all subsequent blocks in the chain cryptographically reference it, reinforcing the integrity of the entire blockchain with each new block added. Tampering with an earlier block requires altering not only that block but also every block after it.

🟦 Hemi Blocks

• In the Hemi Network, blocks are organized into five-minute intervals known as keystones. To inherit Bitcoin’s security, *one Hemi Network state proof must be published to the Bitcoin network every two keystone intervals. *

• The first block of each interval cryptographically references the previous two keystone blocks, ensuring that the network cannot be reorganized without a 51-percent attack against Bitcoin itself, a scenario considered highly unlikely even for powerful entities like nation-states.

🌐 Overview

The Hemi Network utilizes the Bitcoin-Secure Sequencer (BSS), a type of Proof-of-Stake (PoS) node, to achieve consensus, or agreement, on the network’s status. By leveraging the Bitcoin blockchain, the Hemi Network decentralizes its security measures, reducing reliance on internal network validators.

🛠️ How?

⛓️ It incorporates state proofs from the Bitcoin network to validate the Hemi blockchain, ensuring the network's history cannot be easily altered or falsified.

🛡️ The hybrid model provides a unique defense against majority stake attacks, a common vulnerability in pure PoS networks.

🔐 In the event of an overwhelming attack, the network can offload transactions to the Bitcoin network, ensuring continuous operation and security.

🚊 How Bitcoin Tunnels Work

The Bitcoin Tunnels allow Bitcoin assets to move between Bitcoin and Hemi by locking assets in custodial vaults and minting representative tokens on Hemi. Users can freely use these tokens on Hemi, and eventually, tunnel them to Ethereum or other EVM-compatible networks.

Deposit to Hemi

1. Users generate a deposit transaction by sending Bitcoin (or Bitcoin-native assets) to the selected custodianship vault’s Bitcoin address, managed by the multisig.

2. Once sent, the Bitcoin assets are locked in the custodianship vault.

3. Hemi’s Bitcoin Tunnel verifies the successful deposit on the Bitcoin network by monitoring the UTXO table for the corresponding deposit. If the deposit is successfully verified, the system moves to the next step.

4. Upon verification, Hemi mints representative tokens equivalent to the deposited Bitcoin assets. These tokens are sent to the user’s Hemi address. Hemi mints the representative tokens after 6 Bitcoin confirmations, or approximately one hour.

Withdrawal to Bitcoin

1. The user on Hemi initiates a withdrawal transaction by selecting the amount of representative tokens they want to convert back to Bitcoin.

2. These representative tokens are burned on the Hemi network, signaling the system that the user intends to withdraw the corresponding amount of Bitcoin from the custodianship vault.

3. Hemi’s Bitcoin Tunnel updates the rollup state root with the details of the withdrawal transaction. This state root is submitted to Bitcoin by a Publisher to ensure that the withdrawal is accurately recorded.

4. Hemi’s Bitcoin Tunnel verifies the correct burning of tokens and prepares the custodianship system for withdrawal.

5. The custodianship vault is notified of the withdrawal request. In the case of a multisig vault, the required number of signatures is collected to authorize the withdrawal.

6. Once verified, the custodianship vault releases the corresponding Bitcoin or Bitcoin-native assets to the user’s Bitcoin address. It may take up to 12 hours to verify and release withdrawn BTC.

7. The hVM system constantly monitors for any unauthorized withdrawals. In Phase 0, this requires an externally owned account (EOA) to flag any potential issues. In later phases, event notifications will allow automatic detection of unauthorized actions. If any misbehavior is detected during the withdrawal process, the responsible custodian is slashed on Hemi, and corrective measures are taken to prevent unauthorized fund transfers.

🔍 Comparison to Other Bitcoin Interoperability Solutions

• Hemi’s Bitcoin Tunnels leverage the power of hVM (Hemi Virtual Machine) to monitor and secure Bitcoin-based asset transfers.

• The Bitcoin Tunnel contract uses hVM to track Bitcoin addresses and outputs tied to custodianship vaults, ensuring efficient and secure asset management.

• In hVM Phase 0, an externally owned account (EOA) is required to notify the contract of any irregular withdrawals. Once flagged, hVM can verify the offending transaction and respond by slashing misbehaving custodians.

• This contrasts with BTC interoperability solutions like BTC header relay, where users must manually construct cryptographic proofs of misbehavior and relay them to the contract for validation, introducing higher costs and risks of error.

🌐 Overview

• Mining within the Hemi Network involves a specialized process designed to intertwine the security of the Hemi Network with that of the Bitcoin blockchain.

• This is achieved through the operation of the PoP Miner application, which plays a pivotal role in this symbiotic security mechanism.

🛠️ How It Works

1. Fetching Headers: The PoP Miner retrieves network headers from the Bitcoin Finality Governor for Bitcoin blockchain publication.

2. Transaction Construction: The miner constructs Bitcoin transactions embedding aforementioned Hemi Network headers.

3. Proof of Publication: Miners broadcast transactions through the Governor. These transactions are then integrated into Hemi’s consensus layer after being validated via the Bitcoin network, resulting in miner rewards.

⛏️ Run a PoP Miner

💸 Earning Rewards

🕵️ Behind the Scenes

• A Bitcoin Secure Sequencer (BSS) generates and broadcasts a new block.

• BSS nodes send the block header to Bitcoin Finality Governor (BFG) nodes.

• BFG nodes direct the header to PoP Miners.

• Miners create and send back signed Bitcoin transactions containing the header.

• BFG nodes push these transactions into the Bitcoin network.

• Once included in a Bitcoin block, BFG nodes generate PoP Transactions with proofs of Bitcoin inclusion.

• These transactions and Bitcoin headers are incorporated into a new Hemi block by a BSS node, updating the EVM with the latest Bitcoin state.

• Rewards are calculated and distributed to PoP Miners post-mining.

Proof-of-Proof Miners (PoP Miners)

🌐 Overview

• PoP Miners embed Hemi headers — L2 keystones — into Bitcoin blocks, effectively “anchoring” Hemi state to Bitcoin’s security.

• PoP Miners receive Hemi headers from a BFG, create BTC transactions with those headers, and forward them to Bitcoin for inclusion in blocks.

• Successful PoP Miners are earn rewards on the Hemi network, incentivizing them to maintain network operation.

🙋‍♂️ Who might run a PoP Miner?

• Network Miners and Operators: Operators or enthusiasts who want to earn rewards by using their Bitcoin node connectivity. More PoP miners = stronger finality guarantees.

🏁 Requirements

Bitcoin Finality Governor (BFG)

🌐 Overview

• BFG nodes look for Proof-of-Proof (PoP) transactions that embed Hemi headers into Bitcoin, determining if Hemi blocks have attained Bitcoin-level finality.

• BFG nodes serve as the “checkpoint” mechanism for finality by confirming whether competing versions of Hemi blocks exist on-chain and identifying possible reorgs. The nodes then supply Hemi data to PoP Miners, parse resulting PoP transactions and communicate finality info to BSS nodes.

🙋‍♂️ Who might run a BFG node?

• PoP Miners: A custom BFG deamon can notify your local PoP miner and this will broadcast them to your Electrs+bitcoind setup so you don't rely on Hemi Labs — or any third party — which may be congested.

• Enterprise Node Operators: Exchanges, large dApp platforms, or custodial services that need independent, verifiable finality checks on Hemi transactions.

🏁 Requirements

• A PostgreSQL database, bfgd expects the sql scripts in ./database/bfgd/scripts/ to be run to set up your schema.

• A connection to:

  • An Electrs node on the proper Bitcoin network (testnet or mainnet).

  • bitcoind

  • bfgd

Bitcoin-Secure Sequencers (BSS Nodes)

🌐 Overview

• BSS nodes combine Hemi transactions with Ethereum mainnet batches, creating a hybrid solution that inherits Bitcoin security signals (via BFG) and uses Ethereum’s smart contract capabilities.

• These nodes coordinate staking, unstaking, and slashing operations to secure the network, while incorporating finality checkpoints from the BFG. BSS nodes also facilitate cross-chain asset transfers by ensuring that Hemi’s on-chain transactions align with Ethereum-based bridging logic.

🙋‍♂️ Who might run a BSS node?

• Validator/Sequencer Operators: Entities responsible for generating Hemi blocks and maintaining chain consensus.

🏁 Requirements

Modified Geth Node

🌐 Overview

• Hemi Network runs a specialized Geth implementation that supports extended functionalities, enabling seamless interaction between Hemi’s chain state and Ethereum’s mainnet.

• This modified Geth node manages Ethereum transactions and block headers in a way tailored for Hemi’s bridging protocols. The node also consolidates Ethereum state so that BSS nodes (and other Hemi components) can quickly verify or execute cross-chain logic.

🏁 Requirements

🖥️ Nodes 101

• Cryptocurrency networks are powered by a distributed array of computers, each referred to as a node, functioning in a peer-to-peer manner where each holds equal standing. Nodes, depending on the client software they run, fulfill different roles within the network.

• For instance, in the Bitcoin network, full nodes store a complete history of transactions for verification purposes, offering high security, while light nodes, focusing on transaction capability, rely on full nodes for information about the network's current state. This setup allows for a flexible network structure where nodes can freely join or leave without disrupting the network's overall functionality.

🛠️ Hemi Node Structure

• In contrast, the Hemi Network employs a more specialized node architecture to optimize network performance and security. It includes:

  • Bitcoin Finality Governors: Ensures transactions achieve finality on the Bitcoin blockchain.

  • Bitcoin-Secure Sequencers: Orders transactions in a secure manner, leveraging Bitcoin's security.

  • Proof-of-Proof Miners: Validates transactions across blockchains without requiring the entire blockchain data.

  • Modified Geth Node: Manages Ethereum transactions and block headers in a way tailored for Hemi’s bridging protocols.

  • Challengers: Monitors and verifies the correctness of transactions and state proofs (Note: running a Challenger node will be enabled in the near future).

• This segmentation of responsibilities across different node types significantly enhances the Hemi Network's fault tolerance. By isolating specific functions to particular node types, the network ensures that issues within one node type do not compromise the entire network's operations, thereby improving the system's overall reliability.

• This architecture allows user clients to interact seamlessly with both the Bitcoin and Ethereum networks without the complexity of managing diverse node functions.

🔵 EVM Wallets

Key Terms and Concepts

• Private Key: A secret code that allows you to access and control your cryptocurrency in your wallet. It is crucial never to share your private key with anyone, as it grants complete control over your funds.

• Public Address: An address that you can share with others to receive funds. It is a string of alphanumeric characters that acts like an account number on the blockchain.

• Seed Phrase: A series of 12 or 24 words that serve as a backup to restore access to your wallet. This phrase should be stored securely and privately; if lost or compromised, you could lose access to your funds.

• Gas Fees: Transaction fees paid to miners or validators on the blockchain to process and confirm transactions. Fees vary based on network congestion and the complexity of the transaction.

• dApps (Decentralized Applications): Applications that run on a blockchain network rather than a centralized server. MetaMask allows users to interact with dApps directly from their browser.

Ethereum Explorer: Etherscan

Ethereum Networks

The Ethereum network currently comprises a variety of networks with varying functionality, however Hemi build primarily on only two:

• Ethereum Mainnet: The primary Ethereum network where real ETH transactions occur. It is the live network that supports the Ethereum economy and decentralized applications (dApps), with transactions being irreversible and involving real value and fees.

• Sepolia Testnet: A testing environment for Ethereum that mimics the Mainnet but uses testnet ETH with no real value. It allows developers and users to test applications, transactions, and upgrades without risking real funds, providing a stable and efficient testing ground for Ethereum-based projects.

🟠 BTC Wallets

Key Terms and Concepts

• Private Key: A secret code that allows you to access and control your cryptocurrency in your wallet. It is crucial never to share your private key with anyone, as it grants complete control over your funds.

• Public Address: An address that you can share with others to receive funds. It is a string of alphanumeric characters that acts like an account number on the blockchain.

• Seed Phrase: A series of 12 or 24 words that serve as a backup to restore access to your wallet. This phrase should be stored securely and privately; if lost or compromised, you could lose access to your funds.

• Confirmation: The process by which a Bitcoin transaction is included in a block on the blockchain. Each confirmation represents a layer of verification, with multiple confirmations providing increased security against double-spending.

• UTXO (Unspent Transaction Output): A key concept in Bitcoin that represents the amount of Bitcoin available to spend. UTXOs are outputs from previous transactions that have not yet been spent, and they form the balance of your Bitcoin wallet.

• Mempool (Memory Pool): The mempool is a holding area for unconfirmed transactions on a blockchain, where they wait to be included in the next block by miners or validators. Transactions are prioritized based on their attached fees; those with higher fees are typically confirmed faster. Monitoring the mempool helps users gauge current network congestion and set appropriate transaction fees for quicker confirmations.

Bitcoin Address Types

Bitcoin addresses are the unique identifiers used to send and receive Bitcoin. Over time, several address types have been introduced to improve Bitcoin’s efficiency, security, and scalability.

Types of Bitcoin Addresses:

• Legacy (P2PKH): This is the original and most widely recognized address format.

• Nested SegWit (P2SH-P2WPKH): An interim solution that allows the benefits of SegWit while maintaining compatibility with Legacy wallets.

• Native SegWit (bech32): Native SegWit, also known as bech32, introduces significant improvements in transaction efficiency and scalability.

• Taproot: Taproot is the latest upgrade to Bitcoin’s address formats, focusing on enhanced privacy, scalability, and flexibility.

Bitcoin Explorer: Mempool.space

Bitcoin Networks

The Bitcoin network currently comprises a variety of networks with varying functionality, however Hemi build primarily on only two:

• Bitcoin Mainnet: The primary Bitcoin network where real BTC transactions occur. It is the live network that supports the Bitcoin economy and has actual value, with transactions being irreversible and fees applying.

• Bitcoin Testnet: A testing environment for Bitcoin that mimics the Mainnet but uses test BTC with no real value. Developers and users can test applications, transactions, and upgrades without risking real funds. (Not to be confused with Bitcoin Testnet4, a version of Bitcoin Testnet with updated configurations and more stability for testing purposes. It offers an alternative and more reliable test environment compared to the older Testnet3, with no real value attached to the test BTC.

💼 Hardware Wallets

🏁 Prerequisites

📚 Tutorial

Video

1. Visit the Hemi Portal

2. Connect wallet

Click 'Connect Wallets' in the top-right corner of the Hemi Portal.

3. Connect your EVM wallet

Currently, MetaMask and Rabby are the only EVM wallets Hemi supports. Our team is working to add support for additional wallets.

4. Connect to the Ethereum Network

Ensure that you are connected to the Ethereum Network. If you are not connected, the Portal will prompt you to connect.

5. Select asset and enter the amount to tunnel

Use the token dropdown to select the asset you wish to tunnel. After selecting the asset, input the amount of the asset you wish to move to Hemi.

After you have confirmed the gas fee and wish to proceed with the deposit, click 'Deposit.'

6. Confirm the deposit

Sign and confirm your deposit transaction in your connected wallet.

7. You have successfully tunneled to Hemi! 🎉

Your transaction should now be complete! You can check the status and view the transaction in the 'Transaction History' tab.

🔄 Why Use a Third-Party Bridge?

Hemi’s native Tunnel supports a range of popular ERC-20 tokens. However, some assets (e.g., USDC, USDT) are not yet integrated. In these cases, a third-party bridge provides:

• Fast bridging times.

• Established track record of security and reliability.

• Wide token support, including stablecoins like USDC and USDT.

🤝 Supported Third-Party Bridges

Below is a list of third-party bridges you can use to transfer assets to Hemi. Each bridge has its own UI, fees, and specific token support.

🏁 Prerequisites

📚 Tutorial

1. Visit the Stargate bridge

2. Connect wallet

Click 'Connect Wallet' in the top-right corner.

3. Select the asset and confirm networks

Using the token dropdown, select the asset you wish to bridge to Hemi.

4. Enter the amount to bridge

Input the amount of asset you wish to bridge to Hemi.

When you are satisfied with your transaction, click 'Transfer'.

5. Approve and sign the transaction

From your connected wallet, approve the asset spend and sign the transaction.

6. You have successfully tunneled to Hemi! 🎉

After signing the transaction, look for the pending transaction bar at the top of the screen. It may take a few minutes to confirm the transaction.

Follow along with some of the tutorials to help you get a head start when building your first Hemi project.

Wallet Setup

Tunneling

Developer Tooling

PoP Miner

🏁 Prerequisites

1. Add the UniSat Chrome extension

Click 'Add extension.'

📚 Tutorial

Video

1. Open the UniSat Chrome extension

Open the UniSat extension and click 'Create new wallet.'

2. Create a password

3. Copy your secret recovery phrase

After you have saved your private key in a secure area, click 'Continue.'

4. Select address type

Hemi currently uses two primary address types:

• Legacy (P2PKH): PoP mining currently requires a P2PKH address, although this may change at some point in the future.

• Native SegWit (P2WPKH): For everything else on Hemi (i.e., Bitcoin tunneling), any address type can be used but P2WPKH will (generally) be the cheapest fee-wise.

After you have selected your address type, click 'Continue.'

5. Your UniSat wallet setup is complete! 🎉

🏁 Prerequisites

📚 Tutorial

Video

1. Open the MetaMask Extension

2. Access Network Selection Settings

Click on the network-selection dropdown, which is found at the top left of the MetaMask window.

3. Select "Add Network"

4. Add a Network Manually

5. Enter Network Details

In the "Add a network manually" settings, input the following information for the Hemi testnet network:

For Hemi testnet, input the following information instead:

6. Your EVM wallet is ready to go! 🎉

Select Save to add the Hemi network to your MetaMask.

🔄 Switch between Ethereum Mainnet and Sepolia

After you have set up your EVM wallet on MetaMask, you may want to explore some of the unique features on Hemi testnet. This requires switching the connected network in your MetaMask wallet.

🛡️ Against Weak Subjectivity

Even if an attacker gathers old staking keys, they can't alter the state proofs on the Bitcoin blockchain. These state proofs confirm the Hemi Network's transaction history, so any fake blockchain the attacker creates would be recognized as invalid.

🚫 Against Censorship Attacks

In a worst-case scenario where an attacker controls all the sequencers (the nodes that create blocks in the blockchain), the Hemi Network can still function by using the Bitcoin network.

Transactions can be processed (or "offloaded") to Bitcoin, which prevents the attacker from having total control.

🔚 Conclusion

The Hemi Network’s hybrid PoS-PoP consensus model hardens the network protocol against both weak subjectivity and censorship. Even with an overwhelming majority of old staking keys, an attacker would be unable to forge finalized state proofs on the Bitcoin blockchain, and the established state proofs would invalidate the altered Hemi Network chain.

🔄 Why Use a Third-Party Bridge?

Hemi’s native Tunnel supports tunneling BTC, however, some assets (e.g., pumpBTC, iBTC) are not yet integrated. In these cases, a third-party bridge provides:

• Fast bridging times.

• Established track record of security and reliability.

• Wide token support.

🤝 Supported Third-Party Bridges

Below is a list of third-party bridges you can use to transfer BTC assets to Hemi. Each bridge has its own UI, fees, and specific token support.

🌐 Overview

Key Benefits:

• No Slashing Risk – Assets are never used for network validation.

• Flexible Deposits & Withdrawals – No bonding periods; stake and unstake anytime.

• Multi-Asset Support – Stake Bitcoin, Ethereum, and stablecoins assets.

• Ecosystem-Wide Rewards – Earn incentives from Hemi and partner networks.

🔍 How It Works

Hemi’s staking contracts function differently from PoS staking by offering a reward-based deposit model:

• Users deposit assets into smart contracts designed for staking rewards.

• Rewards accumulate over time, distributed by Hemi and integrated partners.

• No lock-up requirements – Users can unstake at any time.

✅ Supported Assets

Hemi’s staking program supports a variety of assets across Bitcoin, Ethereum, and stablecoin categories.

Bitcoin Assets:

Ethereum Assets:

🎁 Rewards

Hemi’s staking program offers rewards based on asset deposits and participation within the ecosystem:

• Earn ecosystem rewards across Hemi and partnered protocols.

• Points-based incentives may apply for early participants and high-value deposits.

• Earn additional benefits on highly-incentivized asset groups.

🌐 Welcome to the Hemi Miner Quickstart Guide!

This guide provides an overview of the essential steps and resources to get you started PoP mining on Hemi.

1️⃣ Explore the Hemi Network

Begin by familiarizing yourself with some of the key Hemi network terms and features.

2️⃣ Set Up Your Wallets

Prepare your various wallets to start PoP mining on Hemi by setting up an EVM and BTC wallet.

3️⃣ Start Mining

❓ What Now?

Congratulations 🎉 Now that you’re PoP miner is running, here are some next steps to deepen your engagement and maximize the potential of your journey on Hemi.

📐Troubleshooting

If you encounter any issues or need assistance at any step, the following resources are available to help:

📖 Background

• Capsule is an asset transfer protocol that allows anyone to batch and transfer multiple assets in a single package on Hemi.

• Additionally, Capsule provides users and developers with advanced functionality like gasless transactions, re-routing/recalling, and configurable security.

🏁 Prerequisites

📚 Tutorial

Video

2. Connect your MetaMask wallet

Connect your MetaMask wallet by clicking the button in the top-right corner.

3. Add assets to your Capsule

Click 'Add Asset' to select the Hemi assets you would like to add to the Capsule. You may add any quantity and any combination of any Hemi assets as desired.

Optional: You may change the name of the Capsule generated in the text box below the 'Add Asset' button.

When finished, click 'Continue'.

4. Add features

Capsule comes with a variety of optional features, including:

• Gasless Pickup: The assets can be redeemed without pay gas costs.

• Time Locked: The assets cannot be redeemed until a specific time.

• Password Protection: A password is required to redeem the assets (a unique and random password is provided by Capsule).

• Asset Key Verification: The asset cannot be redeemed unless the recipient holds a designated NFT in their wallet (specific ID optional).

After selecting and adjusting any preferred features, click 'Continue'.

5. Verify the transaction

Once you are satisfied with your Capsule, click the checkmark that says 'I've read and I agree to the terms listed in the Capsule Terms of Service and Privacy Policy.'

When finished, click 'Continue'.

6. Approve the assets included in your Capsule

To finalize your Capsule, you must approve all the assets you included inside your MetaMask wallet.

When finished, click 'Continue'.

7. Confirm the transaction

Confirm your transaction in MetaMask.

8. All done! 🎉

Copy your Capsule transfer link (and if included, your redemption password) and distribute your Capsule as desired!

🏁 Prerequisites

• Basic CLI Knowledge

📚 Tutorial

Video

1. Binaries

The package you will need to download depends on your OS and architecture:

• Windows (Intel/AMD CPU): heminetwork_v1.0.0_windows_amd64.zip

• Mac (Intel CPU): heminetwork_v1.0.0_darwin_amd64.tar.gz

• Mac (Apple Silicon "M" CPU): heminetwork_v1.0.0_darwin_arm64.tar.gz

• Linux (Intel/AMD CPU): heminetwork_v1.0.0_linux_amd64.tar.gz

• Linux (ARM CPU): heminetwork_v1.0.0_linux_arm64.tar.gz

2. Extract the files

After downloading the necessary files, you must extract them from their compressed format before you can use or access the software. On most operating systems, you can right-click on the downloaded archive and choose "Extract" or similar.

3. Open your CLI and navigate to the extracted folder

Launch your CLI:

Navigate to the folder you extracted by typing cd (don't press Enter yet) and then drag the path of the extracted folder into your CLI, or type the path in manually and then press Enter.

• For example on Linux if you downloaded the package to your Downloads folder and extracted it through the GUI, you might run a command like: cd '/home/<user>/Downloads/heminetwork_v1.0.0_linux_amd64'

4. Confirm folder contents

List the files:

Your output should be:

• Linux & macOS
• For Windows

5. Verify configuration success

To ensure you downloaded the correct binaries and are able to run them, execute the command below:

This will display the help menu for popmd, indicating that it's installed and operational.

6a. Generate public key

6b. Open the JSON

If you chose to generate a new private key in Step 6a, open your JSON to view your file contents.

You should see a result like:

7. Fund your address

Find your wallet address:

• New Address: If you generated a new public key in Step 6a, check the JSON file from Step 6b for your pubkey_hash.

8. Run the Miner

In your console, execute the following commands while:

1. replacing <private_key> with either the value from your JSON file in Step 5 OR your preexisting EVM/BTC private key,

2. replacing <fee_per_vB_integer> with the fee in sat/vB you want to pay.

Linux & macOS

Windows

9. Expected Console Output

10. 🎉 Congrats! You are now a Hemi PoP Miner!

Bitcoin fee/vB

The Bitcoin transaction (normally represented in satoshis per virtual byte or sats/vB) is a fee paid to the Bitcoin miners to include a transaction in a Bitcoin block. It varies with network congestion, typically rising during periods of high transaction volume and decreasing when there is less activity.

• The PoP Miner consumes BTC to pay the Bitcoin miners to include PoP transactions in Bitcoin blocks.

• In order to ensure PoP transactions from your PoP miner are included in Bitcoin blocks, ensure the configured fee is set to an appropriate value. The PoP miner can be configured to use a certain fee in sats/vB by changing the POPM_STATIC_FEE environment variable when running the PoP miner. In a future version, the PoP miner will automatically calculate the current network fee to guarantee PoP transactions are included in Bitcoin blocks.

• The lower you set the fee, the less BTC you will pay per PoP transaction. If your fees are too low, Bitcoin miners may not include your transaction quickly enough for you to successfully PoP mine.

Bitcoin fee determination:

• Set the Static Fee: Re-run the command to set the POPM_STATIC_FEE environment variable from above (export on Linux/macOS, set on Windows) each time you want to change the fee, and restart the PoP Miner afterwards.

🏁 Prerequisites

📚 Tutorial

2. Select the network dropdown

3. Select Bitcoin Testnet

4. You are ready to interact on Bitcoin Testnet! 🎉

Your wallet is now ready to send, receive, and sign transactions on Bitcoin Testnet!

Follow along with some of the tutorials to help you get a head start when building your first Hemi project.

General

hVM & hBK

🌐Overview

Prior to TGE, users who engage in securing Hemi (mainnet) to Bitcoin will receive PoPPoints tokens, which are distributed based on how many other users are actively PoP Mining. These PoPPoints tokens are initially non-transferrable. During the initial mainnet release, all miners who get a PoP publication for a keystone into Bitcoin within ~1.6 hours will share 100 PoPPoints for that keystone round.

As mainnet evolves, this payout algorithm will be adjusted.

📚 Tutorial

Video

1. Open MetaMask

2. Access Token Selection

• Navigate to Tokens

• Click on the three vertical dots on the right of the token menu

• Import tokens

3. Enter the Contract Address

• Type in the tHEMI token contract address 0xC5D2E164601c59c2cD760669e849BFe498003e21 into the Token Contract Address field.

• If the address is recognized, MetaMask will automatically populate the Token Symbol and Token Decimal fields. For PoPPoints, you should see a symbol POPand 18 decimals.

4. Import

• Confirm the accuracy of the provided information, and then click on Next.

• If successful, you should see your PoPPoints tokens in your wallet's token list:

For now, these tokens are non-transferrable.

🌐 Overview

• The web PoP miner was designed for ease of use, allowing users of any experience level to test and run their own PoP miner.

• Due to its lightweight nature, it required no specific hardware, making it accessible from any standard computer.

• While it was not intended for long-term mining operations, it served as an excellent entry point for users interested in transitioning to the more durable CLI version, providing an introduction to Hemi's architecture and its unique integration with the Bitcoin network.

🔐 Security Note

🌐 Overview

• To use hVM directly, you will have to call the appropriate precompile address with the appropriate serialized bytes to pass parameters to the function.

• Each successful precompile call will return serialized bytes according to the precompile’s return data specification.

🟨 Developer Tip

Most dApp developers will use the Hemi Bitcoin Kit (hBK) rather than hVM directly.

• If you’re looking for an easy way to get started developing Bitcoin-aware dApps on Hemi, check out the “Hemi Bitcoin Kit (hBK)” section. Understanding how Bitcoin Kit uses hVM under-the-hood may be helpful, and dApp developers looking to maximize gas efficiency may benefit from using hVM directly to avoid paying overhead for unmarshalling data they don’t need for a specific use case.

⚙️ How It Works

Hemi Virtual Machine (hVM)

The hVM is the backbone of the hBK’s interoperability features, embedding a Bitcoin node within the EVM. This setup allows Ethereum smart contracts to directly query Bitcoin data without relying on external bridges or third-party oracles, ensuring trustless, efficient, and secure access to Bitcoin data.

• Direct Access: Smart contracts can communicate with Bitcoin data embedded in the EVM, enabling them to make queries and receive data via precompiled calls.

• Indexed Data: The fully indexed Bitcoin node maintains transaction history, UTXOs, and meta-protocols like Ordinals and BRC-20 tokens.

Developer Interface: Simplified Interaction with Bitcoin

The hBK abstracts technical complexities, offering developers straightforward methods for accessing Bitcoin data, allowing them to:

1. Directly Pass Data to Precompiled Calls: Simple data serialization/deserialization processes provide a transparent gateway to precompiled Bitcoin calls.

2. Enhanced Query Functions (Upcoming): hBK is set to introduce enhanced functions, combining multiple precompile calls and additional processing steps for advanced operations.

This dual approach ensures developers can create Bitcoin-aware applications without managing low-level integration details, focusing instead on innovation and functionality.

🔑 Key Features

• Embedded Node Access: hBK integrates a fully indexed Bitcoin node within Hemi’s EVM environment, exposing robust Bitcoin data for smart contract use.

• Precompiled Calls for Direct Data Retrieval: Passthrough functions facilitate Bitcoin data queries with direct calls, automatically handling the data structures.

• Enhanced Functions for Advanced Queries: Future upgrades will introduce enhanced functions, combining multiple calls and added processing to support more complex queries and data requirements.

🌐 Overview

• In Proof-of-Stake (PoS) consensus protocols, staking is a form of virtual mining in which users risk some amount of tokens (a “stake”) for the chance to construct a block and earn block rewards. If the staker misbehaves (for example, by trying to cheat the system), the network will remove some or all of the stake (a process called “slashing”). Under normal conditions when stakers act honestly, slashing is a rare occurrence. PoS is a popular alternative to Proof-of-Work (as in Bitcoin) because staking is far less energy intensive than mining.

⚠️ Security Risks in Proof-of-Stake

• Conventional PoS networks, however, face two security risks inherent to staking. If a malicious actor were to acquire more than half of the staking power on the network, he could censor transactions, including slashing transactions, which would prevent other honest validators from regaining control of the network. PoS systems also suffer from weak subjectivity.

• If a malicious actor acquired enough old PoS keys to have the majority of staking power, he could use the old keys to create a valid alternative chain. Pure PoS chains like Ethereum rely on social consensus to address these issues because the protocols themselves are vulnerable.

🌐 Overview

• Proof-of-Proof (PoP) is the Hemi Network’s additive consensus protocol, building on Bitcoin’s consensus for superior security. PoP miners publish cryptographic network-state proofs to the Bitcoin blockchain, protecting Hemi consensus with Bitcoin's proof of work.

• Hemi blocks achieve finality typically nine blocks (approximately an hour and a half) after their proofs are published to Bitcoin.

⏱️ Finality Delay in the Hemi Network

• The Hemi Network accounts for fluctuations in Bitcoin's transaction fees and block timings, recognizing that network-state proofs might not appear in every block.

• To manage this variability, a finality delay of nine Bitcoin blocks is implemented.

If no competing fork publishes proofs to Bitcoin during this period, the network assumes finality, requiring a 51% attack on both the Hemi and Bitcoin networks to alter this.

🌐 Overview

• A cryptocurrency transaction fundamentally represents an update to the network's decentralized ledger.

• Such a transaction mandates a cryptographic signature from the sender's wallet, serving as a verification mechanism to authorize the transaction. Within the Bitcoin ecosystem, scripting capabilities enable the execution of more complex transaction types.

• Conversely, Ethereum operates as a distributed virtual machine, allowing for the execution of sophisticated programs known as smart contracts. These contracts, embedded directly on the blockchain, can operate autonomously based on their programming.

⚖️ The Blockchain Trilemma and L1 Challenges