RGB++ Layer: Building a Bridge Between BTCFi and the UTXO World

In July 2024, CKB announced the official launch of RGB++ Layer, marking the transition of the RGB++ protocol from theory to a practical engineering product, and it will introduce more specific application scenarios. The RGB++ Layer quickly became the focus of industry attention with its vision of building a BTCFi ecosystem among UTXO public chains such as BTC, CKB, and Cardano.

RGB++ Layer is based on the RGB++ protocol, utilizing homomorphic binding and Leap technology to provide a "no cross-chain bridge" full-chain interaction experience for RGB++ native assets or inscriptions/runes across UTXO-based public chains like BTC, CKB, and Cardano. It leverages the Turing-complete smart contract environment of CKB to establish the necessary conditions for Bitcoin to enable asset issuance and the realization of complex DeFi functionalities.

Thanks to the comprehensive account abstraction ecosystem of CKB, the RGB++ Layer can be compatible with Bitcoin accounts and wallets, creating a good experience for Bitcoin users and paving the way for the large-scale application of BTCFi.

RGB++ Protocol: The Theoretical Foundation of RGB++ Layer

The RGB++ protocol was released in January this year, and its core idea is to replace the "client-side verification" of the RGB protocol with on-chain verification on the CKB blockchain. Essentially, it uses CKB as a decentralized indexer, responsible for tasks such as data storage and asset source verification, with CKB serving as the verification layer and DA layer for the RGB protocol to address the shortcomings of the RGB protocol in user experience and support for DeFi.

RGB++ introduces the concept of homomorphic binding, using Cells on the CKB chain as the data carrier for inscription/runic assets, and establishes binding relationships between Cells and UTXOs on the Bitcoin/Cardano/Liquid chains, allowing RGB++ assets to inherit the security of these UTXO public chains and prevent double spending.

This binding approach is similar to how bank accounts in reality need to be linked to a mobile phone number and an ID card. For example, when Alice transfers TEST tokens to Bob, a declaration can be generated that binds the Cell storing the TEST asset information with Bob's Bitcoin UTXO. If Bob then transfers the TEST tokens again, the bound Bitcoin UTXO also needs to be transferred synchronously.

Isomorphic Binding and Leap: Asset Issuance and Bridge-less Cross-chain Layer of BTCFi

To understand homomorphic binding and Leap, it is necessary to first understand the CKB's Cell model. A Cell is an extended UTXO that includes fields such as LockScript, TypeScript, and Data. LockScript is similar to Bitcoin's locking script and is used for permission verification; TypeScript is akin to smart contract code; Data is used for storing asset data.

When issuing RGB++ assets on CKB, a Cell needs to be created, and the token symbol and contract code must be written in the relevant fields. These Cells can be split and transferred like Bitcoin UTXOs. Since Cells are structurally similar to Bitcoin UTXOs and CKB is compatible with the Bitcoin signature algorithm, users can manage CKB chain assets using a Bitcoin wallet.

The core of isomorphic binding is to allow the use of accounts from different public chains such as BTC and Cardano to modify RGB++ asset data on the CKB chain. The Leap function is based on isomorphic binding technology, enabling the switching of RGB++ asset bound UTXOs, such as switching from Bitcoin UTXO to Cardano UTXO, thereby transferring asset control from the BTC account to the Cardano account.

From the user's perspective, this is equivalent to cross-chain asset transfer, but in reality, the data is still stored on the CKB chain; it has only changed its usage rights. This method is more concise than the traditional Lock-Mint cross-chain model and also avoids reliance on mapped asset contracts.

Wrapper

To address the limitations of RGB++ assets as inscriptions/runes on public chains like Bitcoin and Cardano, the RGB++ Layer introduces the concept of Wrappers. Taking the rBTC wrapper as an example, it bridges BTC to the RGB++ Layer and monitors the behavior of bridge guardians through smart contracts. If a guardian engages in malicious behavior, their collateral will be forfeited. If guardians collude to steal locked BTC, rBTC holders can receive full compensation.

![Interpretation of the four major features of RGB++ Layer: The hub of BTCFi and the UTXO world](https://img-cdn.gateio.im/webp-social/moments-7e2b4a6ab2d7fb0255de529f5e1a5652.webp01

Combining Leap and Wrapper, various assets in the BTCFi ecosystem, such as RGB++ native assets, BRC20, ARC20, runes, etc., can be cross-chain to other layers or public chains.

![Interpretation of the four major characteristics of RGB++ Layer: The hub of BTCFi and the UTXO world])https://img-cdn.gateio.im/webp-social/moments-cc2405212d722c0d210006287b795453.webp(

CKB-VM: The Smart Contract Engine of BTCFi

CKB provides CKB-VM for the RGB++ Layer, allowing any programming language that supports the RISC-V virtual machine to be used for contract development on the RGB++ Layer. Developers can efficiently and securely develop and deploy smart contracts using familiar tools and languages within a unified smart contract framework and execution environment.

![Interpretation of the four major features of RGB++ Layer: The hub of BTCFi and the UTXO world])https://img-cdn.gateio.im/webp-social/moments-d328261e897b284bd3a728b967e4aafc.webp(

Native AA Ecosystem: Seamless Integration of BTC and RGB++

RGB++ Layer reuses the native AA solution of CKB, aiming for compatibility with major UTXO public chains like BTC and Cardano at both the developer and user levels. Users can directly operate assets on the RGB++ Layer using accounts, wallets, or authentication methods such as BTC, Cardano, or even WebAuthn.

![Interpretation of the four major features of RGB++ Layer: The hub of BTCFi and the UTXO world])https://img-cdn.gateio.im/webp-social/moments-2658eb38334c112a460d1782bb891361.webp(

For example, the CCC wallet middleware supports mainstream wallet entries such as Unisat and Metamask. Eco wallets like JoyID in the CKB ecosystem implement WebAuthn, allowing users to authenticate their identity through biometrics, achieving seamless and high-security login and identity management.

![Interpretation of the four key features of RGB++ Layer: The hub of BTCFi and the UTXO world])https://img-cdn.gateio.im/webp-social/moments-87c5cf1c169bfe7833b8aa124cf52336.webp(

Conclusion

RGB++ Layer serves as an important infrastructure for memecoins such as inscriptions/runes/dye coins, enabling on-chain interaction scenarios. Its smart contract execution environment built on RiscV provides a development space for the complex business logic required by BTCFi. In the future, we will continue to monitor the progress of RGB++ Layer and conduct a more in-depth analysis of its related technological solutions.

![Interpretation of the four major features of RGB++ Layer: The hub of BTCFi and the UTXO world])https://img-cdn.gateio.im/webp-social/moments-70743e47826b1cebacacd7fb59c38200.webp(

![Interpretation of the four major characteristics of RGB++ Layer: The hub of BTCFi and the UTXO world])https://img-cdn.gateio.im/webp-social/moments-834b2d8dd535292d1a0f07c6301584ea.webp(

![Interpretation of the four major features of RGB++ Layer: The hub of BTCFi and the UTXO world])https://img-cdn.gateio.im/webp-social/moments-81647df165a5a169361750ddbed05339.webp(