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Although the cryptocurrency industry pioneer, bitcoin has faced challenges in recent years keeping up with the ever-changing world of blockchain. Compared to other blockchains, bitcoin is slow, expensive, and lacking in features like smart contracts that are now underpinning the industry.
Layer 2 (L2) solutions have emerged to address these challenges, bringing upgrades and improvements to the bitcoin network.
Blockchains consist of an execution layer and a consensus layer. The execution layer manages users’ transactional activities, while the consensus layer protects and validates these transactions. Conceptually speaking, the execution layer maintains the blockchain activity while the consensus layer maintains the blockchain’s identity. The structure of an L2 is typically to improve the functionality of the execution layer while being sufficiently connected to the consensus layer.
In short, let the blockchain do more while still being the same blockchain.
Examining L2s requires understanding what capabilities they add this to bitcoin. Because the basic ideas and terms of this technology have alienated many bitcoin enthusiasts, this guide aims to help users grasp Layer 2 solutions by explaining their functionalities and types.
Upgrading Bitcoin
L2s enhance the bitcoin network by removing inherent limitations such as high fees, low speeds, and lack of smart contracts — all qualities which favor an unhackable, uncensorable maximum security model, as well as decentralization — qualities which will not be surrendered by the base layer. Improvements to blockchain execution capabilities are generally described in terms of scalability — the amount of transactions that can be processed on the blockchain in any given time period.
Because “scaling” a blockchain is too broad a descriptor for the variety of functionalities added, this section instead breaks down the main improvements to the execution layer and what this means in terms of what bitcoin can do.
Faster And Cheaper
Due to its transaction fees and block size limitations, bitcoin’s native chain is expensive and slow. These limitations are cited as the main bottleneck inhibiting broad functionality and adoption. Layer 2 solutions, at the most basic level, seek to solve this problem. They try to increase the network’s speed and output while keeping fees as low as possible.
The most obvious use case for making bitcoin faster and cheaper is microtransactions. Microtransactions are the small frequent transactions people make everyday. No one will use bitcoin to buy a coffee or a toothbrush if the transaction fee is half the total cost and takes 30 minutes to be confirmed.
The most popular and oldest layer 2 for bitcoin focuses on exactly this problem. The Lightning Network allows users to conduct micro-transactions with minimal fees and almost instant confirmation times. Reducing the cost and speed of transactions allows for the everyday usage necessary for mass adoption, such as tipping, small purchases, or running a business that accepts bitcoin.
Smart Contracts And DAPPs
Smart contracts are computer programs built on a blockchain that automatically execute a set of rules. The distributed computing power of the underlying blockchains executes a smart contract in a decentralized manner. Smart contracts can be used to make a digital agreement between parties with no third party to authorize the terms. Further, smart contracts are the foundation of decentralized applications (DAPPs). These are computer applications that use the decentralized execution technology in a blockchain to run programs without a centralized third party.
Smart contracts are the essential infrastructure powering the entire decentralized economy, all its platforms, tools, and organizations run on these programs. Bitcoin was not originally designed to support complex smart contracts and their development requires much higher TPS than bitcoin can natively mange. Therefore, things like DeFi and DAOs have traditionally been exclusive to smart contract-compatible blockchains such as Ethereum.
However, Layer 2 solutions can use their increased throughput and additional programmability to add such capabilities to bitcoin. For example, Rootstock and Stacks are layer 2 solutions that support smart contract execution, enabling the development of a decentralized infrastructure on bitcoin.
How Layer 2 Solutions Work
Layer 2 solutions function by transferring some computational execution off the main blockchain while maintaining a connection to the native bitcoin network. The methods for doing this can be broadly categorized into sidechains, state channels, and roll-ups.
Although there is additional nuance to many layer 2 solutions and not all fit perfectly into these categories, such distinctions allow for a general picture of the core types of layer 2s.
Sidechains
Sidechains are independent blockchains that run in parallel to the bitcoin main chain.
Sidechains that have some systematic dependence on the native chain, this dependence is generally seen through a pegging mechanism. Users lock their bitcoin on the main chain, which is then mirrored by minting equivalent assets on the sidechain. This relationship between the blockchains allows users to interact with the sidechain’s unique features (such as smart contracts) while still being anchored to the bitcoin network.
Further, sidechains often have their own consensus mechanisms, such as Proof of Stake or federated consensus, to secure the network independently of the bitcoin main chain. Through these consensus mechanisms, such chains can create their own incentives for participation, such as alternative rewards or their own native tokens.
Notable Side Chains:
- Rootstock: This sidechain introduces smart contract functionality to bitcoin, allowing developers to build dApps and more complex financial instruments.
- Liquid Network: Liquid focuses on fast and confidential transactions, particularly beneficial for exchanges and traders needing quick and private transfers.
- Stacks: Stacks is a blockchain and cryptocurrency for smart contracts, decentralized finance, non-fungible tokens, and dApps.
State Channels
State channels allow participants to conduct multiple transactions off-chain and then record the final state on the bitcoin blockchain. This process significantly reduces the number of transactions that need to be processed on-chain.
State channels maintain a connection to the bitcoin network through multi-sig addresses. With these addresses, multiple parties must sign off on a transaction, ensuring that off-chain transactions are secure and agreed upon by all involved parties. This method provides a secure link to bitcoin by ensuring that off-chain transactions within the state channel can be finalized and enforced when added to the main chain. Additionally, state channels will use security entities like “Watchtowers,” who are users that monitor the network for malicious activity and receive rewards.
The most well-known implementation of state channels for bitcoin is the Lightning Network. Here two parties open a channel by locking a certain amount of bitcoin into a multi-signature address. Once the channel is open, they can conduct unlimited transactions off-chain. Only the final state of the channel is recorded on the bitcoin blockchain network.
Rollups
Rollups work by aggregating multiple transactions into a single batch. Rollups interact with the bitcoin network by periodically committing aggregated transactions to the main chain. This process ensures that the state of the rollup is consistent with the main chain.
There are two main types of rollups: optimistic rollups and zero-knowledge rollups (zk-rollups).
- Optimistic rollups: These are “optimistic” because they assume transactions are valid and only perform a check if a dispute is raised. This approach minimizes immediate computational load but requires a mechanism to handle disputes effectively.
- zero-knowledge rollups These use cryptographic proofs to verify transactions according to minimal information about the transaction. This method retains higher privacy and speed, although it can be more complex and dangerous to implement.
Rollups are just starting to be seen on Ethereum and other blockchains, while implementation with bitcoin is still in the conceptual stage and has yet to be launched outside of research.
Challenges For Layer 2s
Despite the variety of use cases and the serious commitment by most of the bitcoin community, Layer 2 solutions face several challenges.
- Security risks: While Layer 2 solutions aim to enhance security, they also introduce new attack vectors. For instance, rollups must handle potential fraud disputes, and sidechains need to ensure their consensus mechanisms are resistant to attacks.
- Complexity: Implementing and maintaining Layer 2 solutions can be complex. Developers need to ensure seamless integration with the bitcoin network while maintaining usability and security.
- Interoperability: Different Layer 2 solutions often operate independently, which can lead to fragmentation. Ensuring interoperability between various Layer 2 solutions is a significant issue that needs to be addressed to realize the full potential of these technologies.
The Obvious Solution
It is almost universally agreed upon that Layer 2 solutions are needed for bitcoin to reach mass adoption. By enabling microtransactions and smart contracts, they expand bitcoin’s use cases to compete with the latest blockchain movements.
A basic understanding of the mechanisms of rollups, sidechains, and state channels, along with their security measures and connectivity to the bitcoin network, is essential for users to navigate emerging projects. Bitcoin Layer 2 solutions represent a crucial evolution in the bitcoin ecosystem, as they allow bitcoin to reclaim its role as the foundation and center of the blockchain industry.