Title: OP_CAT, the Heatedly Discussed New Proposal: What Impact Will It Have on the BTC Ecosystem?
Author: Haotian
CryptoInsight
How should we view the recently discussed Bitcoin proposal, OP_CAT? Although it has not yet been officially merged into the Bitcoin Core code, it has sparked widespread discussion within the BTC community.
So, what problem does the OP_CAT opcode aim to solve? If implemented, what improvements will it bring to BTC’s programmability? And what impact will it have on the future market evolution of the BTC ecosystem? Let’s briefly discuss my understanding:
Table of Contents:
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What is OP_CAT?
What Goals Can OP_CAT Achieve?
What Changes Can OP_CAT Bring to Bitcoin?
Does OP_CAT Benefit BitVM?
OP_CAT is a new opcode proposal, jokingly referred to by developers as being in a quantum entanglement superposition state between BIP420 and BIP347. The specific EIP is not important; it is enough to understand that this is a proposal still under discussion and not officially adopted. In simple terms, OP_CAT allows for the combination and processing of multiple UTXO unlocking script byte string fragments. It can enhance BTC’s mainnet programmability, program scalability, and on-chain verification computational complexity.
Similar to the Covenant contract as a Bitcoin script extension proposal, OP_CAT also aims to enhance Bitcoin script’s extensibility. The difference is that the Covenant’s goal is to enable more complex programmability of Bitcoin transactions to support complex smart contracts and application scenarios. In comparison, OP_CAT aims to simplify the construction and execution of complex scripts to improve on-chain verification efficiency.
Layman’s understanding: OP_CAT provides the ability to combine script fragments. Prior to its introduction, each UTXO script was executed independently. With OP_CAT, we can split a complex execution logic into a series of simple script fragments, which can be stored in different UTXOs and created by different transactions. When complete execution is required, all nodes concatenate these script fragments in sequence using the OP_CAT command to trigger execution.
With this combination ability, theoretically, Bitcoin can have many complex execution logics, such as:
1. Multisignature with time locks, which can involve multiple entities, multiple UTXOs, and complex execution unlock conditions set by time locks.
2. Recursion and looping, allowing multiple script byte string fragments to form recursive and conditional execution, continuously looping until a termination condition is met.
3. Modular applications, where common script logic can be extracted and reused in multiple program execution fragments. For example, Alice transfers money held on platform C to Bob, requiring the signatures of three entities. If the signing time exceeds the limit, Alice and Bob can jointly sign to retrieve the funds. If Bob fails to sign for a long time, Alice can withdraw the transaction. If Bob suspects an issue with the source of Alice’s funds, he can refuse to accept them, and so on. This is just a simple example. In reality, the combination of script fragments can be used to achieve more complex and granular control.
Previously, BitVM executed complex operations off-chain, only implementing crucial verification and settlement paradigms on-chain, which sparked great imagination regarding BTC’s programmability and Turing-complete computing. OP_CAT’s “recursive” combination execution on the BTC mainnet is another supplement to this imagination. Moreover, OP_CAT has many benefits, such as accelerating the implementation of BitVM, reducing on-chain verification costs, and expanding the ecosystem and developmental synchronization of UTXO-bound chains.
How to understand this? Previously, to execute BitVM, the off-chain program needed to be encapsulated into independent script fragments that could be executed by a single UTXO. The off-chain construction cost was high. Executing and assembling these fragments on-chain would also require a more complex TaprootTree structure. This means that the cost of on-chain interaction and verification for BitVM would be relatively high. After the introduction of OP_CAT, the fragments packaged by BitVM off-chain no longer need to be able to execute independently in each case. On-chain, UTXO unlock conditions can accumulate to a certain extent before performing a summary and updating the status. Clearly, the combination of script fragments can greatly reduce the number of interactions and costs required for on-chain verification.
In conclusion, the heated discussion surrounding OP_CAT contains everyone’s expectation for further enhancing Bitcoin’s programmability. If it truly becomes a reality, it will catalyze the implementation of BitVM, enhance the security of various BTC Layer 2 cross-chain asset solutions, expand the ecosystem and mainnet development of UTXO-bound chains, and even advance potential scalable markets such as the Lightning Network and RGB client verification. Theoretically, any improvement in BTC’s programmability will have an immediate stimulating effect on its extended ecosystem. After all, everyone is trying to build an oasis in the desert, and if one day the sand becomes a concrete floor, building a skyscraper will undoubtedly be much easier.
However, will it be truly merged and adopted? Considering the previously proposed but unadopted Covenant proposal, using the OP_CAT new proposal to imagine some market possibilities is also a good idea.
