Everything must start with the Bitcoin expansion battle.
At the earliest, Satoshi Nakamoto had a block size limit of 32MB in the code, but because the block size of the block was very small at the beginning of Bitcoin's operation, Satoshi Nakamoto set a capacity of 1MB in September 2010 limit.
In the same year, an early developer suggested that the Bitcoin block size should be expanded to 7.1MB. Satoshi Nakamoto replied that directly changing the code will cause compatibility problems (hard forks). It is recommended to change it later if necessary.
Until February 2013, this suggestion was posted again, and the issue of capacity expansion became a hot topic on bitcointalk. At this time, the average Bitcoin block size was 150KB (1MB=1024KB), and many people began to discuss the issue of block limitation of 1MB. However, Satoshi Nakamoto disappeared a long time ago, and the related rights of Bitcoin development have been handed over to Gavin Andresen (Gavin got the management rights and decentralized it to several developers).
From here, the discussion about block caps and hard forks began.
"Love"-BCH is born
The expansion group and the Core group (Core developers are not all opposed to expansion, but the overall voice is against) expansion has started, and the battle lasts for four years. Because there are so many things that have happened in the past four years, it is impossible to explain clearly to you one by one, so I will select the more important stages (not completely in chronological order) for your understanding.
In May 2015, when the average block size reached 400KB, Gavin proposed to expand to 20MB (BIP100) in March 2016. However, the proposal met with a lot of opposition. Part of the opposition came from Chinese mining pools (the proportion of Chinese mining pools was already very high at the time), and most mining pools believed that the synchronization delay of large blocks would be greater, which would affect revenue. The other part of the opposition came from some other core developers.
Soon, Core said that it can rely on the development of sidechains and other solutions + segregated witness to solve part of the expansion problem. Gavin's main push to increase the block limit and the core developers who control the development sovereignty formed a disagreement.
At the beginning of 2016, blocks frequently appeared full blocks (1MB). On February 22, 2016, a Hong Kong meeting was held. Chinese miners reached an agreement with several Core developers and Blockstream CEO to realize Segregated Witness soft fork + 2M expansion. Known as the Hong Kong consensus. However, the Hong Kong consensus ended in failure.
In the same year, Gavin publicly declared that CSW was Satoshi Nakamoto. After a series of events, the entire Bitcoin community believed that CSW was a liar and Gavin became an accomplice. The reputation plummeted and the expansion period led by Gavin ended in failure.
Subsequently, the formation of Bitcoin Unlimited became a new hope for the expansion group and received wide support, including some support from China's mining industry. However, because Bitcoin Unlimited's technology is not enough, it is far worse than Core, and there have been several big bugs, which caused everyone to lose confidence, but the expansion party began to receive support from the mining pool.
The bull market started in March 2017, Bitcoin began to be congested, and expansion was imminent. In May, the New York Consensus Conference was held and everyone re-reached the consensus of Segregated Witness + 2MB expansion.
The community's call for the realization of segregated witness is increasing. Core developers have proposed UASF (User Activated Soft Fork BIP148). It is recommended to bypass miner voting directly and activate Segregated Witness directly on August 1.
In order to prevent the failure of the New York consensus (worry that the Core group only activates Segregated Witness and does not expand the capacity by 2MB), in June, Bitmain proposed UAHF (User Activated Hard Fork) to respond. Said that as long as UASF is implemented, the UAHF hard fork will be implemented immediately.
At the end of June 2017, Bitcoin ABC proposed a feasible version of UAHF (the block size was expanded to 8MB), and it was supported by Wu Jihan, Bitcoin Jesus Roger, Yang Haibo and others. The end of UAHF is now BCH.
On August 1, 2017, BCH was born. Important figures in the Bitcoin community such as Gavin and CSW have successively entered the BCH community.
Looking back on this history, it is not difficult to find that BCH is actually the result of the growth and advancement of the expansion group that started from Gavin.
"Hate"-the battle for computing power: BSV is born
As mentioned earlier, the Bitcoin ABC development team proposed a viable UAHF, so there is now BCH. The parties who originally supported the expansion gathered in the BCH community (part of the expansion group), starting from the united "love" to "hate".
In the next year, BCH development was supported by teams such as Bitcoin ABC, BU, Bitprim, nChain, Bitcrust, ElectrumX, Parity and Bitcoin XT. But among these teams, the ABC team has the most actual control over the BCH community, and the development leadership is still in the hands of ABC.
In August 2018, Bitcoin ABC announced that it would upgrade BCH on November 15th, hoping to develop BCH in the direction of the infrastructure public chain and open up more application scenarios.
The specific updates include:
1. Add standardized transaction sorting (CTOR) to transactions in the block
2. Add two opcodes OP_CHECKDATASIG and OP_CHECKDATASIGVERIFY.
However, the nChain faction led by CSW did not agree with this. In mid-August, CSW and nChain announced the creation of Bitcoin SV and launched a new upgrade plan, hoping that BCH will adhere to Satoshi Nakamoto's philosophy and focus on the transfer transaction itself.
The plan also gives two updates:
1. The upper limit of block capacity has been increased from 32MB at the time to 128MB
2. Restore 4 opcodes that were designed by Satoshi Nakamoto in earlier versions but were disabled
Both parties have strong opinions on each other's updates and cannot reach an agreement.
Let me talk about the first upgrade of ABC, changing topological sorting (TTOR) to canonical sorting (CTOR). The simple explanation is because Bitcoin adopts the UTXO model, and utxo is closely linked with each other and has a relatively strong dependence. And CTOR, not according to the logical relationship, sorted by the hash value of TXID. The ABC team believes that TTOR will burden the node because the node has to calculate an effective ordering, which may be an obstacle to performance. CTOR will simplify subsequent verification. However, CSW believes that CTOR's recent improvements to the BCH system are not obvious and are unnecessary improvements.
The upgrade of BSV mainly emphasizes raising the upper limit of 32MB block capacity to 128MB. It is hoped that this will increase the BCH capacity and network throughput and make it easier for BCH to be commercialized. The main reasons for the ABC's objection are that the actual capacity of each block of BCH is currently around 200kB, and the current 32MB block upper limit is 160 times the actual capacity, and there is no market demand for capacity expansion. Second, the 128MB large block lacks corresponding test data. Large blocks will increase node pressure.
This is the divergence caused by the two distinct lines and is the inevitable result of the intensification of the contradictions between the almighty radicals headed by ABC and the fundamentalist conservatives headed by CSW in the BCH community.
In this context, a battle of computing power started.
In the end, BCH has split into two chains, one is BCH-ABC, and the ABC side inherits more resources from BCH, including the support of large ecological nodes, and retains the title of BCH; the other BCH-SV, which is now BSV.