March 1, 2024

An easy-to-understand interpretation of BEVM technical solution

BEVM is a Bitcoin L2 solution entirely built on Bitcoin's native technology.

Following the Bitcoin Taproot upgrade in 2021, the BEVM team developed a fully decentralized Bitcoin layer2 technology framework based on Schnorr signatures + MAST(Merkle Abstract Syntax Tree) and other Bitcoin native technologies. The BEVM Canary network has been operational for 8 months (launched in July 2023), with over 100,000 on-chain users, 6 million on-chain TXs and more than 30 projects in its ecosystem, covering 15 different tracks including $BTC stablecoins, DEX, Lending, etc. It is one of the few Bitcoin L2 solutions that has launched the Canary network.

Leveraging years of exploration and accumulation in the Bitcoin L2 space, the BEVM team was among the first to identify the core proposition of Bitcoin layer2: how to achieve decentralized cross-chain mechanism for $BTC. Based on Bitcoin's native technology, the BEVM team proposed a fully decentralized $BTC cross-chain solution, providing a solid technical foundation for the implementation of Bitcoin layer2.

History of BEVM Team in Bitcoin L2

The BEVM team has six years of experience in developing and operating Bitcoin L2 solutions. In 2018, the core team of BEVM introduced ChainX, employing Bitcoin's 15-signature multisig and Bitcoin light nodes to achieve $BTC cross-chain bridge, ultimately facilitating the cross-chain of over 100,000 $BTC.

However, the 15-signature multisig solution was still relatively centralized and did not address the complete truthfulness issue of $BTC cross-chain, until the Bitcoin Taproot upgrade at the end of 2021.

The 2021 Taproot upgrade brought two core BIPs to Bitcoin: Schnorr signatures and MAST, offering a new vision for a fully decentralized Bitcoin L2 solution to the BEVM team.

Schnorr signatures, an aggregate signature technique, offer higher efficiency, smaller storage requirements, and better privacy than elliptic curve signatures. While Bitcoin's maximum multisig address count based on elliptic curve signatures is 15, Schnorr signatures allow for expanding this count to 1,000. Managing $BTC with 1,000 multisig addresses on the blockchain consumes only a single Gas fee while ensuring the privacy of all multisig addresses.

(Explanation of the Schnorr Aggregate Signature Scheme)

When Satoshi Nakamoto created Bitcoin in 2008, Schnorr signatures were not yet open-sourced (they were open-sourced in 2009), leading him to opt for elliptic curve signatures. After 12 years of development and validation, Schnorr signatures were proven more suitable for Bitcoin, leading to their formal introduction into Bitcoin by the Bitcoin Core team, opening a new chapter for Bitcoin's scalability.

Schnorr signatures could expand Bitcoin's multisig address count from 15 to 1,000, enabling more decentralized management of Bitcoin.

MAST(Merkle Abstract Syntax Tree), introduced in the Bitcoin Taproot upgrade, can be understood as an equivalent smart contract instruction set. With MAST, the 1,000 multisig addresses powered by Schnorr signatures do not need to rely on individuals for signing but can be driven by MAST contracts. Thus, the introduction of MAST contracts eliminated the need for multiple signers, driving the smart and code-based management of multisig addresses without human intervention, moving closer to complete trustlessness for $BTC cross-chain and management.

(Operating Logic of MAST Contracts)

While MAST + Schnorr signatures achieved the decentralization of the $BTC multisig address count and the codification and smart management of multisignature, the question remained: who would drive the MAST? The answer cannot involve humans. Only through network consensus can MAST truly achieve trustlessness, enabling network consensus to manage and spend Bitcoin in a decentralized approach.

Therefore, the BEVM team innovatively integrated Bitcoin light nodes into the L2 as verification nodes, merging Bitcoin L1 Taproot multisig addresses with the L2 Bitcoin light nodes. These Bitcoin light nodes serve as both the block-producing nodes of the BEVM network and the custodians on Bitcoin Mainnet. For example, when the network consensually decides to transfer 10 $BTC from a BEVM address back to the Bitcoin mainnet, the L1 Taproot multisig addresses will automatically execute a 10 $BTC transaction through MAST. Note that this $BTC cross-chain and management process involves no human participation and is entirely driven by network consensus, achieving true trustlessness.

In summary, the core of BEVM's Bitcoin L2 solution is based on Bitcoin's Schnorr signatures to achieve the decentralization of the number of multisig addresses (expandable to 1,000 multisig addresses); based on Bitcoin's MAST to realize the codification and smart management of multisignature (eliminating human involvement); and based on the Bitcoin light node network to facilitate communication between Bitcoin Mainnet and L2, ultimately relying on network consensus to drive Bitcoin's multisig and management, achieving a truly decentralized Bitcoin L2 solution.

It's worth mentioning that since the block-producing nodes in the BEVM network are all Bitcoin light nodes, if Bitcoin ceases to exist, so will the BEVM network. The BEVM network cannot exist independently from the Bitcoin  network, making BEVM a true Bitcoin L2 solution, not a sidechain as misunderstood by some in the market.

Why is achieving decentralized $BTC cross-chain so crucial for Bitcoin L2?

As is well known, Bitcoin's highly simplistic UTXO design and limited block space cannot support smart contracts or complex scenario expansion. To achieve true scalability, $BTC must leap to a L2 network to handle complex scenarios. Therefore, decentralizing the $BTC Bridge to L2 is the first step all Bitcoin L2s must take. If decentralized $BTC cross-chain cannot be achieved, such so-called Bitcoin L2 solutions are built on an untrustworthy foundation, with their asset security and future development prospects naturally questionable.

However, most current so-called Bitcoin L2 solutions completely avoid discussing how to address the fundamental issue of $BTC cross-chain, instead lightly emphasizing the L2 technical jargon, such as ZK-rollup or OP-rollup. First and foremost, whether ZK-rollup or OP-rollup, Bitcoin nodes will not verify these data, rendering them meaningless. Even if these could make the L2 ledger somewhat trustworthy, the issues of how to manage and secure user assets in a decentralized $BTC cross-chain remain unavoidable.

BEVM, built on three core $BTC native technologies: Schnorr signatures, MAST contracts, and the Bitcoin light node network, perfectly solves the problem of secure decentralized $BTC cross-chain, breaking through the core proposition of Bitcoin L2.

To better build the Bitcoin ecosystem and robustly expand the Bitcoin L2 track, BEVM will fully open source its Bitcoin L2 solution. After the mainnet launch, BEVM will introduce BEVM-Stack, i.e., a modular Bitcoin L2 feature, allowing anyone to build their own Bitcoin L2 with just one click based on BEVM-Stack. BEVM has already constructed a fully EVM-compatible Bitcoin L2 modular technology stack.

In the future, as the ecosystem develops, BEVM will also build technology stacks compatible with the StarkNet network's Cairo language, Solana's Rust language, and the MOVE language, aiming to bring $BTC into any chain through BEVM. This allows any blockchain innovation technology to be utilized by $BTC, maximizing both the value of $BTC and the benefits of blockchain technology, thereby establishing a BTC-native superchain network with BEVM as the technology stack.