Bitcoin Classic Publishes Code That Could Double Bitcoin's Block Size

The first release for an alternative implementation of bitcoin that would double its transaction capacity has been published.

Today, bitcoin users run or rely on versions of Bitcoin Core, the descendent of the original bitcoin software developed by its pseudonymous creator Satoshi Nakamoto. Yet the ongoing debate on how to increase capacity has opened the door to other implementations of bitcoin to gain prominence, as previously demonstrated by the rise and subsequent fall of Bitcoin XT.

The release

of Bitcoin Classic, which constitutes a repackaging of the latest Bitcoin Core software with support for bigger blocks, indicates what could perhaps be a new phase in the ongoing debate whether or how to scale the bitcoin network’s transaction capacity. It follows the release of a second beta version last week.

For over a year, members of the bitcoin development community, users and business interests have engaged in a wide and often bitter debate about the block size.

The latest proposal, in the form of Bitcoin Classic, would raise the maximum size of transactions blocks from a 1 megabyte (MB) limit to a cap of 2 MB. If activated, the new software would constitute a split in the bitcoin network, each with its own divergent transaction histories after the point of divergence.

Since it was unveiled last month, Bitcoin Classic has attracted both supporters and detractors who, depending on their point of view, say it represents either the next phase for bitcoin development or a threat to its very existence.

So far, the proposal, which would effectively split the existing history of bitcoin transactions into two (one with 2 MB blocks and one with 1 MB blocks), has garnered significant support from startups working in the bitcoin space, as well as a number of bitcoin miners.

Discussions about the proposal, as well as the broader issue of whether to increase the transaction capacity on the bitcoin network, have raged on social media for weeks. The debate has effectively split bitcoin’s active Reddit community in two, and further debate has taken place on Twitter as well as individual Slack channels dedicated to Core and Classic.

What comes next?

Now that Bitcoin Classic has been released, one question remains: Will it actually be adopted?

Preliminary data suggests that the number of nodes running Bitcoin Classic is on the rise. According to node data site Coin.Dance, there are more than 500 nodes running the software at press time, compared to roughly 4,100 running Bitcoin Core.

Yet for the software to 'activate', the code requires that the last 751 out of 1,000 blocks be mined that support 2 MB blocks. Once that happens, a 28-day period will begin in which node operators and miners would need to replace their software in order to be compatible with Bitcoin Classic once the larger blocks start being processing.

On a conference call today hosted by bitcoin services startup Coinbase, which pledged its support to operate Bitcoin Classic nodes, original Bitcoin Core maintainer Gavin Andresen said that he expects miners that don't immediately support Classic will move quickly to do so as the anticipated support ramps up.

"Once you get to 75% of miners, the remaining 25% come along very, very quickly," he said. "We’ve done these...not exactly this type of upgrade but we’ve done similar types of upgrades in the past, so we do know what’s likely to happen. And so once miners see that all the other miners are going in a certain direction, they have an incredibly strong incentive to follow."

Going forward, adoption depends on a majority of node operators and miners taking the step to break away from the existing network. To date, new versions of the bitcoin software have been rolled out via voluntary soft forks.

The Bitcoin Classic team, which counts among its members developers Andresen and Bloq CEO Jeff Garzik, said that it expects to release another version based on Bitcoin Core 0.12 in the next few weeks.

With the release also comes an updated list of developers and contributors. In addition to Andresen and Garzik, developers include Pedro Pinheiro, Tom Zander and Jon Rumion.

Jonathan Toomim, who was listed at the top of the developer list on earlier versions of the Bitcoin Classic site, is now listed as an "external advisor" alongside Ledger editor Peter Rizun.

Former Bitcoin Foundation board member Olivier Janssens is listed as a "facilitator", and Final Hash CTO Marshall Long is said to be providing support on the mining side, though his name was previously removed from the Bitcoin Classic site.

Debate to continue

Supporters of a block size increase say that a capacity boost is needed in the near-term to make room for more transactions and stave off what they call prohibitively high transaction fees.

Those backing Bitcoin Classic say that competition among implementations of bitcoin is needed in order to spur development and create a greater degree of choice for users.

Opponents say the changes proposed are too fast and too risky, given what they say are lingering questions about how a hard fork – wherein nodes are required to download new software or risk being effectively cut out of the network due to incompatibility – could be successfully conducted.

Questions have also been raised about aspects of the governance system proposed for Bitcoin Classic, the introduction of two functioning blockchains that share years of transaction history and each with its own network of assets, and the exact degree of support from bitcoin miners for Bitcoin Classic versus a broader block size increase, particularly those based in China.

At the same time, there appears to be support among developers in the bitcoin community for some form of capacity increase, including a raising of the block size.

Bitcoin Core developers and supporters have rallied around a proposal called Segregated Witness that changes how signature data is included in transactions. This proposal has its detractors as well, who say that it adds unnecessary complexity to the network.

Overall, the debate has proven to be as acrimonious as it has been divisive. Accusations that Bitcoin Classic essentially constitutes a coup, as well as allegations that Bitcoin Core is acting at the behest of the startup Blockstream, have thus far colored the nature of the debate in recent weeks.

Today’s release is unlikely to change this state of affairs.

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