Since its release on August 6th, Bitcoin XT, a patch set on top of the existing Bitcoin Core, has focused the bitcoin community’s attention on the block size debate. Core maintainers and highly influential CEOs alike, like Peter Smith of Blockchain and Steven Pair of BitPay, have entered the online fray, fueling passion-laden discussions across Reddit, Twitter, Medium, and GitHub.
Multiple solutions have been proposed to alleviate the block size debate, like 8MB blocks, 20MB blocks, and dynamic block size limits, among others. However, Bitcoin XT is gaining traction as a viable solution as it would create a hard fork in the protocol by permanently splitting the blockchain into two different ledgers. This fork will occur if 75% of miners adopt the new patch after January of 2016, and at that time, nodes running outdated versions of the software will not accept the valid larger blocks. One of the chief criticisms leveled at Bitcoin XT is the low threshold for adoption, with many core devs suggesting that 90% or 95% threshold for adoption would optimal. As of August 16th, 7.2% of all nodes were running Bitcoin XT, with the count growing steadily. Current statistics are available, updated hourly.
Gavin Andresen, Chief Scientist at the Bitcoin Foundation, and Mike Hearn, the creator of Bitcoin XT are the chief proponents and the public faces of the patch, actively engaging with those who do not support an increase to the block size limit. Andresen developed the current patch to Bitcoin XT, which implements his BIP101 proposal. Under BIP101, the maximum block size will increase from the current 1MB to 8MB, and will double every 2 years after that until it reaches 8,192MB.
In addition to an increased block size limit, Bitcoin XT includes several other changes to Bitcoin Core such as double spend relaying, anti-DOS measures, support for new apps that use partial transactions such as the Lighthouse crowdfunding app, and DNS seed changes.
Since Bitcoin XT is a patch to the current infrastructure, Core users will not be forced to redownload the entire blockchain. It is also important to note that at this time, running Bitcoin XT is equivalent to running Core. Bitcoin XT will create a hard fork from the current Core implementation only if a 75% majority is achieved.
Critics of Bitcoin XT often point to the inherent technical risks of a hard fork. In addition, many experts, including three out of the five Core developers, believe that an increased block size limit would cause significant problems for bitcoin’s infrastructure down the road. The larger blockchain, they argue, would force certain nodes to shut down as storage space requirements become unfeasible for privately owned nodes. As nodes close due to climbing costs, the network could shrink towards centralization.
“I strongly urge that we return to the existing collaborative constructive review process that has been used for the last 4 years which is a consensus by design to prevent one rogue person from inserting a backdoor, or lobbying for a favored change on behalf of a special interest group, or working for bad actor” said Bitcoin Core developer Adam Back in an email.
Current attempts to debate Bitcoin XT’s feasibility, unfortunately, have been censored in many discussion forums. A single moderator on the Bitcoin subbreddit has been caught deleting “hundreds of, what appear to me, to be perfectly valid comments,” according to /u/jratcliff63367, another moderator. Since Bitcoin XT would create an alternative blockchain that’s incompatible with the current bitcoin blockchain, several moderators have called Bitcoin XT an alternative cryptocurrency and removed posts discussing the changes on the Bitcoin subreddit, instructing users to discuss the topic in alternative forums.
Despite the passionate conflicts, rational heads seem to have prevailed. As core developer Mark Friedenbach commented in a post, “[T]he block size limit should be raised, but only in step with what can reasonably be accomplished with engineering improvements to ensure a decentralized, policy neutral network. There are many in this space working to identify criteria for that, and a couple of different proposals for actually raising the limit in a way that would be more sensitive to these issues. All that we ask for is the time for due process, not ultimatums and hostile forks.”
Photo Martin Sharman / Flickr (CC)