Bitcoin proposal BIP-420 proposes to restore the OP_CAT opcode

Golden Finance reports that the Bitcoin improvement proposal BIP-420 officially proposes to restore the OP_CAT operation code to introduce the "Covenants" function on Bitcoin. OP_CAT advocate and Taproot Wizards co-founder Udi Wertheimer said that OP_CAT will allow smart contracts, secure cross-chain bridges, on-chain transactions, zero-knowledge proof verification and other functions to be implemented on Bitcoin. So-called "constraints" are advanced scripting features that can set specific conditions for the use of Bitcoin in future transactions. This will open up many application scenarios, such as creating secure vaults that allow transaction rollback, automating recurring payments, setting up scheduled transfers for scenarios such as inheritance, and complex financial instruments such as custody and bonds. The proposal, written by Ethan Heilman and Armin Sabouri, aims to restore OP_CAT by redefining the opcode OP_SUCCESS126 in a backward-compatible way for a soft fork. However, whether the OP_CAT soft fork can be realized depends on multiple considerations such as technology, security and community consensus. The concept of Bitcoin “constraints” dates back to at least 2013. In addition to OP_CAT, there are also multiple "constraint" proposals such as CTV, CSFS, and LNHANCE, which are currently in different stages of research and discussion.