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Technical deconstruction of CKB public chain: Why can it speed up BTC's legitimacy Layer2?

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CKB’s chain-native features and underlying architecture innovation compatibility will allow it to go further in this BTC layer2 non-standard melee

Original author: Haotian, crypto researcher

When I first heard that @NervosNetwork was fighting a desperate battle to be the BTC layer2, I was not surprised. Because the CKB public chain technology is close to BTC and ahead of BTC, it can not only inherit the native UTXO features, but also achieve more advanced programmable feature expansion. If it is almost impossible for the CKB public chain to surpass BTC, then the next best thing is that it will definitely be invincible as the BTC layer2. Why? Next, let's talk about my opinion on CKB.

The current BTC layer2 market is limited by the defects of the BTC main network in verification capabilities, and a situation of blooming flowers has emerged. That's right, it is precisely because the script language of the BTC mainnet is inherently simple, and its computing + verification capabilities are almost close to 0, that the market has been given space and opportunities to fully play. At present, in addition to limited transaction verification + multi-signature within the UTXO unlocking conditions, the BTC mainnet cannot directly implement all other complex transaction logic such as data and state change diff that need to be verified, and can only use BTC as an asset settlement layer, and then extend a powerful public chain to build local consensus and computable verification capabilities to achieve expansion. In this way, there is no unified standard for the implementation of BTC layer2, there is no such thing as "orthodoxy", and it is even difficult to distinguish between high and low. The only way to distinguish between the narrow and broad senses is according to the perception of the community: In a narrow sense, only the extension schemes under the lightning network state channel and the one-time seal of RGB are the real BTC orthodox layer2, because they fully apply and give play to the limited script verification capabilities of BTC, and do not require or rely on the minimum off-chain local consensus. Generally speaking, as long as the local consensus of the extension chain is recognized and there is a cross-chain bridge solution to ensure the safe migration of assets, in theory, the current Ethereum EVM chain, Solana high-concurrency performance chain, etc. can serve as BTC's layer2. Obviously, the current BTC layer2 market is obviously polarized, either extremely narrow, like the Lightning Network and RGB, which are slow and difficult to develop, or extremely broad, all performance chains that can achieve safe asset interaction with the BTC main network can be called BTC layer2. So, is there no "compromise" solution? Yes, the answer is: the technical underlying framework uses the UTXO model and the performance has been adapted and upgraded @NervosNetwork . Specific performance:

1) CKB Network and BTC are completely the same in "UTXO model, mining consensus mechanism", etc. Unlike the account balance model of mainstream public chains such as Ethereum, UTXO has certain unique advantages. It has certain advanced features in transaction privacy, flexible transaction construction, and parallel processing to prevent double spending. It can be called Satoshi Nakamoto's greatest invention. This also explains why Sui and Aptos adopted a similar UTXO model after Ethereum. We can say that Bitcoin's capacity and block speed have limitations of the times, but the UTXO model is very advanced. CKB has adopted the UTXO model and optimized and upgraded it to the Cell model, which not only retains the transaction purity of the Bitcoin UTXO model, but also provides the data status of account models such as Ethereum. To understand it in layman's terms: the creation and destruction of the Bitcoin UTXO model is similar to the process of coins being continuously destroyed and minted, while Cell removes the destruction process and wants to verify and preserve the status for a long time. Each Cell contains two fields: Capacity and Data. Capacity is equivalent to the balance of UTXO in bytes; Data stores all historical transaction status and other data in any form. This allows the Cell collection to not only accurately express the balance and process asset transfers, but also include a series of complex states of smart contracts. In general, the Cell model is a leading transaction model that is more sustainable and flexible, and can expand the scope of application of the UTXO model. It is also the key for CKB to inherit the security of the BTC main network while "speeding up" the slow expansion of Bitcoin such as the Lightning Network and RGB. 2) Take the recent launch of RGB++ by CKB as an example. According to the normal process, the difficulty of the BTC ecosystem to extend a mature RGB solution is not the one-time sealing process of the BTC main network, but the process of communication, coordination and joint maintenance of the status between the off-chain client verification nodes, especially when the nodes are decentralized. In other words, the RGB theory looks easy, but the implementation is limited by the limitations of basic infra and other restrictions, which leads to many obstacles.

CKB saw this clearly and simply let all these nodes doing off-chain client verification participate in the on-chain public verification process of CKB. This directly accelerated the UTXO extension client practice path that RGB wanted to achieve. After all, it is difficult to reach a consensus in a complex P2P node network in an off-chain client environment, which is full of complexity and challenges. For example, off-chain communication may face data synchronization delays or inconsistencies, and there are also some fraud and attack challenges. If this process can be copied to the on-chain environment, it will be simpler. 3) RGB++ has been discussed a lot recently. I will add an Open Transaction data format proposed by CKB, and everyone will feel the advanced characteristics of the CKB chain. In short: Open Transaction allows multiple participants to build and aggregate different transactions at different times, including three major features: partial construction, modification allowed, incremental construction, and aggregation. For example: Alice creates an Open Transaction, declaring how much token A she wants to exchange from Bob in exchange for token B. After the transaction is initiated, it is still editable. After receiving it, if Bob agrees to the transaction conditions, he can add his own token B and supplement the transaction conditions. At first glance, it sounds very abstract. For example, in a cross-chain scenario, Alice and Bob can independently complete asset transactions on different heterogeneous chains, which greatly improves the cross-chain interoperability of the CKB chain; in a complex DeFi transaction scenario, the DeFi in which users participate may need to be dynamically adjusted according to market changes. Through Open Transaction, contract participants can flexibly adjust transaction conditions during the contract execution process, which undoubtedly greatly enriches the complexity handling capabilities of transactions.

In my opinion, the unlocking conditions of Open Transaction and UTXO transactions are exactly the same. They can integrate the construction of complex transaction unlocking conditions, multi-party signature participation, complex application scenarios and other transaction environments together, which is also a value innovation that follows the BTC main chain idea. What's interesting is that @busyforking, a member of the Ethereum core R&D team, used BTC's UTXO model for his first work. Although Ethereum's smart contract model is now more widely used, Jan and his Nervos team chose to extend and upgrade BTC's UTXO model. It not only expresses awe for Satoshi Nakamoto's minimalist UTXO transaction model, but also sows the seeds for it to become BTC Native layer2.

To sum up: I am very optimistic about CKB doing BTC layer2. In the short term, it can indeed speed up the implementation of Lightning Network and RGB on the UTXO model chain, and at least provide a meaningful reference for the expected implementation of these two types of orthodox expansion solutions on the BTC mainnet; in the long term, CKB's chain-native characteristics and underlying architecture innovation compatibility and other characteristics can enable it to go further in this BTC layer2 non-standard melee.

Note: There are still many technical details and highlights about CKB. More content will be further analyzed when there is time. I can't help but sigh that BTC layer2 has given some new chains the opportunity to rise from the ground, and also given old chains unlimited possibilities to sprout new buds.