The Shared Security Model: How Bitcoin Secures Layer 2 Blockchains

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Bitcoin’s monolithic infrastructure has built a formidable reputation in the cryptocurrency community for its impenetrable security.

Since bitcoin’s launch in 2009, it has proven to be a predictable, resilient, and efficient network for processing electronic peer-to-peer (P2P) payments, just as Satoshi Nakamoto hoped.

“Bitcoin is backed by the largest computer network in the world, a network orders of magnitude larger than the combined size of the clouds that Amazon, Google, and Microsoft have built over the last 15–20 years.” — Cathie D Wood, Founder of ARK Invest

However, as bitcoin’s popularity grew, scalability issues became increasingly pressing concerns for the nascent blockchain. To galvanize its own extreme security standards, the bitcoin protocol forfeited flexibility in favor of decentralization, which makes adapting to changing circumstances, and onboarding billions of users, much more challenging.

To address these scalability challenges, Layer 2 blockchains (L2s) have begun building on top of bitcoin’s core architecture and offering much more enhanced services to users. Rather than competing with bitcoin’s base layer (as “alt” coins attempt), all of these L2s rely on bitcoin’s design to secure their operations, forming one of the most unique — and potentially most disruptive — symbiotic relationships in the cryptocurrency space.

Thanks to “shared security” with bitcoin’s blockchain, a new generation of L2s is poised to supercharge bitcoin’s growth and create a new ecosystem of decentralized finance (DeFi) built on bitcoin’s blockchain.

What Is “Shared Security” On Bitcoin?

The concept of “shared security” in the cryptocurrency industry refers to using an established blockchain, like bitcoin, as the basis for building secondary add-on projects. Rather than creating separate, self-sovereign blockchains with distinct features and functionalities, L2s leverage the security standards of a Layer 1 network, dramatically reducing their development time, resource expenditure, and technical requirements.

In the case of bitcoin, new decentralized projects settle transactions on bitcoin’s payment ledger, which also means they inherit the decentralization, size, and legacy of bitcoin’s proof-of-work (PoW) mining algorithm. Since L2s fall back on the bitcoin blockchain, they have greater freedom to create more innovative and scalable solutions for their users.

How Are L2s Using Shared Security On Bitcoin?

Each L2 has distinct technical specifications, but these protocols conduct all of their transaction processing and data storage off of the bitcoin blockchain (aka “off-chain”) to provide a faster and cheaper alternative to the bitcoin base chain. The “shared security” aspect kicks in whenever L2s interact with bitcoin’s blockchain to finalize transaction data or resolve disputes. Periodically, L2s send transaction information to the bitcoin mainnet for final processing, giving these secondary networks enhanced legitimacy.

For example, some bitcoin L2s include “anchoring” protocols, in which nodes regularly compile a list of transactions and attach a cryptographically verifiable hash function before submitting them to the bitcoin blockchain. It’s also common for L2s to use snapshots or “rollup” solutions — including Zero-Knowledge Succinct Non-Interactive Argument (ZK-SNARKs) or optimistic rollups — to provide irrefutable data on transactions to the main blockchain. ZK-SNARKs involve creating “validity proofs” by solving advanced computational problems off-chain and attaching them to the transaction data, whereas optimistic rollups assume all incoming transactions are valid and allow nodes to dispute information before final approval.

As an example, the Lightning Network (LN) operates as a fast and low-fee L2 using the bitcoin protocol. When users open an account on the LN, they create an off-chain “state channel” with other LN participants, and they’re free to send their bitcoin as an IOU to other users throughout the L2. Whenever LN users want to redeem the bitcoin in their account, they close their state channel and settle their transaction history on bitcoin’s official, i.e., Layer 1, final payment ledger. Even though LN traders have to pay bitcoin network fees to open and close their LN accounts, they’re free to send bitcoin as many times as they want within the LN to enjoy fast and virtually feeless transfers.

What Are The Benefits Of Bitcoin Shared Security?

Although the name “shared security” emphasizes the secure foundation bitcoin provides for L2s, that doesn’t mean the bitcoin base layer isn’t benefiting from this arrangement. Rather than leeching off of bitcoin’s software design, L2s play a massive role in scaling bitcoin’s operations and introducing more use cases for the world’s largest cryptocurrency.

Strong Foundational Layer Security

Shared security opens the doors for up-and-coming decentralized projects to take advantage of the oldest and largest PoW blockchain. Not only does this foster development on innovative and emerging Web3 projects, it provides bitcoin with a way to offer its high security standards to global developers. The more L2s that build using bitcoin as their base layer, the greater bitcoin’s reputation grows as the “ground floor” for all Web3 security, potentially providing the foundation for future activity in sectors like DeFi, GameFi, and non-fungible token (NFT) trading.

Scalability, Speed, And Efficiency

L2s have the power to process far more transactions off-chain and to batch data using cryptographic hash functions and rollups. Plus, since these L2s take some of the transactional burden off of bitcoin’s shoulders, they naturally reduce congestion on bitcoin’s main chain, further decreasing the risk of network congestion and bottlenecks. By spreading cryptocurrency transactions throughout multiple L2s, bitcoin boosts its transaction throughput, translating to a more enjoyable user experience with lower odds of slow transfer speeds or high fees.

Liquidity In DeFi

Another benefit of linking L2s to bitcoin through shared security is that these secondary applications help seamlessly connect bitcoin to the wider world of Web3. Specifically, L2s open the possibility of using bitcoin in DeFi applications, including decentralized borrowing, liquidity pools on decentralized exchanges, and liquid staking. The more interconnected L2 protocols become — and the more convenient they make the transfer experience — the easier time traders have using bitcoin as the basis for their DeFi activities.

With the introduction of liquid re-staking services like the Lorenzo Protocol, it’s also possible to use bitcoin to create liquid staking derivatives (LSDs) and participate in DeFi yield opportunities. The transferability, interoperability, and tokenization features offered on L2s help make bitcoin a premier DeFi asset, thus driving more liquidity into Web3 protocols.

Innovation

L2s let bitcoin take care of the processes required to secure a decentralized network, which allows developers to free up their imaginations to ponder what else is possible in Web3. Beyond DeFi, L2 programmers have already begun exploring wild use cases on top of bitcoin, including preserving classic Nintendo video games on-chain and creating a fiat-denominated stablecoin with bitcoin as the basis. Bitcoin’s high security standards allow a fresh wave of developers and cryptographers to use this blockchain as their starting base when exploring the outer reaches of decentralized technology.

Using Bitcoin’s Shared Security For Superior Scalability

With shared security, bitcoin “shares” many of its intangible value propositions (i.e., its longevity, trustworthiness, and battle-tested resilience) with the broader cryptocurrency community. At the same time, the L2s relying on these attractive traits boost bitcoin’s potential by effectively distributing transactions, improving network efficiency, and expanding the use cases for bitcoin.

These numerous benefits make bitcoin shared security the ultimate “win-win” in cryptocurrency. L2s enjoy the increased safety of bitcoin’s blockchain, and bitcoin enjoys an enhanced efficiency while expanding its reach into Web3. Even in these early stages of development, it’s safe to say shared security will play a pivotal role in realizing a more fully bitcoin-based digital economy in the near future.

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