Bitcoin Classic, the Bitcoin implementation set to double Bitcoin’s 1 megabyte block size limit by a hard fork, suffered a significant setback shortly after its official release this week. A group of prominent exchanges, mining pools and other industry players organized under the “Bitcoin Roundtable” collective, stated publicly they will not switch to Bitcoin Classic for the present.

Open Letter

An open letter by the Bitcoin Roundtable, including signatories representing major Bitcoin exchange Bitfinex, ASIC-manufacturer and mining pool BitFury, exchange, wallet service and mining pool BTCC, cloud hashing service Genesis Mining, mining pools F2Pool, BW Pool, Ghash.IO and others, states:

“We think any contentious hard-fork contains additional risks and potentially may result in two incompatible blockchain versions, if improperly implemented. To avoid potential losses for all bitcoin users, we need to minimize the risks. It is our firm belief that a contentious hard-fork right now would be extremely detrimental to the bitcoin ecosystem.”

Bitcoin Classic requires a 75 percent hash power activation threshold to activate a block size limit increase. Since the Bitcoin Roundtable collective accounts for more than 60 percent of hash power on the Bitcoin network today, activation seems unlikely unless some of the signatories reverse their positions.

Instead, the letter expresses support for an initial block size limit increase through Segregated Witness. This solution, which was made a first step in Bitcoin Core‘s scalability “roadmap,” offers an effective block size limit increase of .6 megabyte to 1 megabyte, along with additional improvements. As one of its main benefits, Segregated Witness can be rolled out as a soft fork, meaning only miners need to upgrade, rather than all nodes on the Bitcoin network.

The letter reads:

“We see the need for a modest block size increase in order to move the Bitcoin project forward, but we would like to do it with minimal risk, taking the safest and most balanced route possible. [Segregated Witness] is almost ready and we support its deployment as a step in scaling.”

Bitcoin Roundtable

Bitcoin Classic was first introduced a month ago by former Bitcoin Foundation board member Olivier Janssens, FinalHash CTO Marshall Long and Bitcoin miner and developer Jonathan Toomim. Shortly after Bitcoin XT lead developer Mike Hearn very publicly denounced Bitcoin a failed experiment, the alternative implementation quickly gained support from major Bitcoin industry players including Coinbase, Blockchain and Bitstamp, as well as Bitcoin Core veterans Gavin Andresen and Jeff Garzik.

Several major mining pools initially endorsed Bitcoin Classic as well, but this support has been nuanced since. In the midst of a crisis atmosphere, mining pools and other companies organized several meetings across the world as well as online to discuss the situation. One of these meetings, the Bitcoin Consensus Round Table organized by BitFury a day after the North American Bitcoin Conference in Miami, formed the basis of what later resulted in the Bitcoin Roundtable letter.

Speaking to Bitcoin Magazine, BitFury CIO Alex Petrov explained:

“BitFury was ready to support the Bitcoin Classic initiative – but this doesn’t mean we planned to immediately start mining in favor of Bitcoin Classic or run Bitcoin Classic nodes. We do believe a hard fork block size limit increase must happen, but we ultimately want to avoid too much confrontation among miners, or a split within the community. This is not helping to move the Bitcoin project forward in any way. Rather, we should have a constructive conversation, start talking, get the perspectives from both sides of the debate. That way everyone can get a deeper understanding of potential issues, and we will be able to find solutions.”

This call for unity was seconded by cloud hashing service Genesis Mining CFO Marco Krohn.

“There is huge split in the community regarding the block size limit. The dispute has been going on for a while, first with Bitcoin XT and now between Bitcoin Classic and Bitcoin Core. But I think it’s important to realize that both sides want Bitcoin to succeed; assuming anyone has bad intentions is not helpful,” Krohn said.

And, regarding concrete scaling proposals:

“Segregated Witness is a great idea, and almost everyone supports it. However, it’s only a one-time capacity increase. There were several official and unofficial attempts to convince the Bitcoin Core development team to add a 2 megabyte block size limit increase hard fork to the roadmap, and be more specific about its implementation – but to no avail so far. The letter is an attempt to calm the situation, and to continue the constructive conversation with the Bitcoin Core development team. We are optimistic to find a solution which better addresses the needs of the businesses, miners and the rest of the community.”

China

Previously, a subset of the Chinese mining community – most notably including major ASIC-manufacturer and mining pool Bitmain/AntPool – offered Bitcoin Core an alternative proposal. Rather than switching to Bitcoin Classic, involved companies proposed to raise the block size limit to 2 megabytes, but with a 90 percent hash power support requirement. This sentiment was later echoed by Bitmain co-founder Jihan Wu, who said that AntPool will test Bitcoin Classic but does not support rolling out a hard fork block size limit increase in the short term. And, on its own Internet forum, Bitmain clarified it will not vow loyalty to any development team in specific:

“We applaud the [Bitcoin] Core team’s increased communication and willingness to find compromise, but we do not wish to bind ourselves to a document that does not contain concrete technical proposals. We look forward to reviewing Bitcoin Core’s updated roadmap and evaluating it on its technical merits, but we do not believe that this should be done to the exclusion of other development efforts.”

One of the driving forces behind the Bitcoin Roundtable letter, BTCC COO Samson Mow, acknowledged he does not expect a sudden switch to support Bitcoin Classic from mining pools, if there is any switch at all. Rather, he explained that the Bitcoin Roundtable has even broader support than the letter suggests.

“Bitcoin Classic often overstates their support, or misconstrues support for 2 megabytes or a hard fork as support for Bitcoin Classic,” Mow said. “Some companies not on the signatory list have given a commitment to not run Bitcoin Classic until we see if Bitcoin Core can adapt. They support the Bitcoin Roundtable, but they would have preferred a more strongly worded request to Core, and so have refrained from signing. That was the compromise we reached.”

Mow agreed the main goal right now is to get more clarity from Bitcoin Core on the proposed scalability roadmap, and said the Bitcoin Roundtable group will help to facilitate as needed.

Mow:

“Everyone is asking for a hard fork, but no one is talking about what exactly will go into the hard fork. Is it cleaning up the code a Segregated Witness soft fork left behind? Is it an increase to 2 megabytes or more? What will be the requirements for activation? We need to have those discussions together.”

Bitcoin Classic

While the Bitcoin Roundtable letter was a setback, Janssens, listed as “facilitator” in the Bitcoin Classic release notes, has not given up hope for Bitcoin Classic. Addressing visitors of the r/btc subreddit, predominantly frequented by bitcoiners in favor of a hard fork block size increase, Janssens made clear that Bitcoin Classic intends to remain active – even if it does not achieve a hash rate majority in the short term.

“Classic is here to stay. We finally have a great competing client with a lot of traction,” Janssens said. “Don’t let the recent letter discourage you. We still have double digits coming on board of Classic soon, and the rest will follow quickly when the fee event will take place in the next weeks. We cannot run away from reality, and the time for more talk and debate is over. The block size limit will be hit very soon.”

Additionally, at least one mining pool so far stated public support for Bitcoin Classic. Slush Pool, accounting for some 4 percent of total hash power, has committed to let individual miners vote on a potential block size limit increase.

Speaking to Bitcoin Magazine, Slush Pool operator Marek “Slush” Palatinus explained:

“I still like Bitcoin XT or even solutions which remove block size limit completely, but consider it a politically dead solution, so there’s no point in pushing it over and over. I therefore support Bitcoin Classic, as it seems to be a trade-off for both camps. And I’m generally not afraid of hard forks much; I’m even a proponent of regular hard forks – say, once a year – which would be able to reflect recent development in [the] field of cryptocurrencies.”

And the Bitcoin Roundtable signatories, in the end, did not completely exclude a switch to Bitcoin Classic at some point in the future either. If after three weeks the Bitcoin Core development team has not addressed concerns raised by the letter signatories, some of them might still opt to make a switch.

BitFury’s Petrov said: