OP_CAT has formally introduced the “BIP-420” proposal due to ongoing controversy surrounding the contract. Bitcoin BTC
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“BIP-420 enables contracts on Bitcoin, allowing for smart contracts, secure bridges, on-chain transactions, zk proof verification, and more,” OP_CAT supporter and Taproot Wizards co-founder Udi Wertheimer posted late Monday. However, it does not appear to be an official Bitcoin improvement proposal.
In general, a commitment in Bitcoin is an advanced scripting feature that allows specific conditions on how Bitcoin can be used in future transactions. This could enable use cases that include the creation of secure “vaults” that allow for reversible transactions, automatic recurring payments, time-locked transfers for scenarios such as inheritance, and complex financial products such as escrows and bonds.
OP_CAT was originally included as one of the first opcodes in Bitcoin. However, pseudonym creator Satoshi Nakamoto disabled this feature, along with several other opcodes, in 2010 due to concerns about the possibility of creating scripts that could lead to vulnerabilities.
Opcode refers to instructions used in the scripting language that forms part of the Bitcoin protocol. A Bitcoin script consists of a series of opcodes, each of which performs a specific task.
This proposal, written by Ethan Heilman and Armin Sabouri, seeks to reintroduce OP_CAT to Bitcoin via a backwards-compatible soft fork by “overriding opcode OP_SUCCESS126.”
This is the same opcode value used in the original OP_CAT, and is designed to eliminate potential confusion by not using different opcode values. This proposal focuses only on reintroducing the opcode without changing any other aspect of the script’s operational limitations.
According to the proposal, the OP_CAT opcode simplifies and extends Bitcoin’s functionality, including making the decentralized protocol more practical and supporting advanced multi-signature setups. In essence, OP_CAT will significantly improve the performance and flexibility of Bitcoin scripting, making it easier to develop more sophisticated applications directly on the Bitcoin blockchain, the authors claim.
However, the likelihood of an OP_CAT soft fork will depend on a combination of technical, security, and community consensus considerations. Without broad consensus and a clear demonstration of safety and usability, the implementation of OP_CAT remains uncertain.
Other Bitcoin Contract Offers
Bitcoin’s covenant concept has been discussed for several years, since at least 2013. Integrating covenants into Bitcoin could greatly expand its functionality, bringing it closer to a programmatically flexible platform like Ethereum, but it could also increase concerns about complexity and potential security risks.
OP_CAT is not the only Bitcoin contract offering on the table, with others including CTV, CSFS, and LNHANCE. Each has different approaches, pros and cons, and requires different stages of research and discussion.
Check Template Verin (CTV), proposed by Jeremy Rubin in BIP-119, introduces a new opcode that ensures that only transactions matching a predefined template can spend Bitcoin, allowing for things like vaults, congestion control, and legacy multi-signature migration. Enabling use cases.
OP_CHECKSIGFROMSTACK (CSFS), proposed by various developers including Rubin, allows signature validation using a message and public key specified in a script, independent of the transaction. CSFS is considered to be in some ways more flexible and powerful than CTV, potentially enabling a wider range of applications.
LNHANCE proposes to add even more flexible scripting possibilities, including loops and conditional execution based on external data. This is a more conceptual and less formalized proposal than the others.
Updated to clarify proposal status.
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