As Bitcoin developers experiment with features and upgrades that increasingly resemble the vibrant activity on alternative blockchains like Ethereum, some of programmers are pushing for a revival of a piece of code that existed on the network in its early days.
A Bitcoin Improvement Proposal (BIP) for a new version of the “OP_CAT” code, introduced in October, aims to restore functionality that was available in early versions of the blockchain’s software but was removed by its elusive and likely pseudonymous creator, Satoshi Nakamoto, in 2010.
The “cat” in the proposed operational code is short for “concatenate” – since technically the function was used to join two elements in a script.
Nakamoto was concerned that OP_CAT exposed the network to security concerns, such as the risk of a denial-of-service (DoS) attack if it were used in conjunction with other opcodes to create very large stack elements. Another concern was the potential for “exponential” memory requirements.
The developers behind the new proposal, BastionZero co-founder Ethan Heilman and Botanix Labs lead software engineer Armin Sabouri, describe their refreshed version of OP_CAT as a simple piece of coding – just a dozen or so lines. They say it could provide the general-purpose functionality that’s been missing from Bitcoin since its very early days, and that’s been a key driver of growth on Ethereum, the second-biggest blockchain. If launched, so-called layer-2 networks might be easier to build atop Bitcoin, along with other innovations like decentralized exchanges or file hosting.
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The developers argue that technological advances since 2010 and other changes to the Bitcoin code have already addressed many of the risks that worried Nakamoto.
“Having worked with Bitcoin for a really long time and having built a number of protocols on top of it, one of the big problems I kept running into is that variables in the programmability of the network can’t really be combined,” Heilman told CoinDesk in an interview.
“My biggest use case for CAT is introducing protocols that have the ability to post something on the layer 1 and have another transaction reference it, showing that one element proves another element and so on,” Sabouri explained.
Such functionality could provide smart contract-like features and trustless bridges to layer 2s, he said.
It would also enhance the building of vaults – a type of Bitcoin smart contract or “covenant” that puts constraints on how a bitcoin can be spent. These systems can help deter hackers or other malicious parties from attacking decentralized apps.
“It’s pretty common in second-layer designs to have to combine things in order to sign or hash them, Merkle trees being a really good example,” Sabouri said. “The fact that you cannot do that in the scripting language of Bitcoin is a pretty big shortcoming.”
The proposal could prove contentious among some members of the Bitcoin community who believe adding functionality to the network is at odds with the blockchain’s original ethos of providing a store of value and a peer-to-peer payments network.
The Ordinals protocol, for example, was a notable development for essentially bringing non-fungible tokens (NFTs) to Bitcoin for the first time, by allowing users to “inscribe” data on chain. However, the congestion that the inscriptions caused, and the premium they added to fees, drew ire from some Bitcoin purists.
Luke Dashjr, an influential Bitcoin developer who has mounted campaigns to fight what he terms as “spam” transactions on the 15-year-old blockchain, told CoinDesk in a direct message that he is “not familiar enough with the use cases for OP_CAT to comment on it specifically right now.”
“Building on Bitcoin is fine. Attacking Bitcoin (eg, “ordinals”) is not,” Dashjr wrote.
“There is the camp that believes Bitcoin should entirely ossify and not change much because its such a vital piece to this core new money system,” André Neves, co-founder and chief technology officer of Bitcoin payments company Zebedee, told CoinDesk via email. “Other camps/devs believe Bitcoin is far from ready to ossify, as there’s a lot more to be added/fixed/improved.”
“There are people who want Bitcoin to work forever just how it is working now,” Heilman said. “I don’t think they are wrong; it’s just a question of the philosophy and the direction that the greater community wants to go in.”
OP_CAT might indirectly help to relieve network congestion, according to the authors.
“We need to be looking at how we can get Ordinals onto a second layer, so it’s on a…
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