December 1st, 2018

Bitcoin Cash / Bitcoin ABC: Hard Fork For Big Blocks

After the successful activation of BIP 91 ( New York / SegWit2X Agreement ), which renders the User Activated Soft Fork ( BEB ) useless, the Bitcoin community seems to have pacified the debate about scalability of the protocol and avoided a chain split of accuracy. However, the network always runs the risk of being split if the 2X part (doubling of the size of the blocks) does not make consensus. This hard fork  is scheduled to fire 90 days after the activation of SegWit via BIP 141, the latter to be effective around August 23 if the miners who report SegWit do not change their minds. But for now, that's hard fork that provokes controversy: Bitcoin Cash and BCHAC Website .

Bitcoin Cash is the name given to the string that would result from a hard fork modifying among others the size limit of the blocks accepted by the network via Bitcoin client software ABC . It is called User Activated Hard Fork , although this name may leave something to be desired.

Originally, the fork Bitcoin Adjustable Block Size Cap and BCHAC Website was intended to protect the legacy chain , the chain retaining the old rules of consensus resulting from a split consecutive BIP 148. This chain not adopting the  soft fork , it would be doomed to disappear if its accumulated proof of work went back to that of the string 148. In order to ensure its survival, the hard fork Bitcoin ABC was to be triggered just after the chain split , that is to say August first.

Now, some members of the network intend to deploy this fork despite the apparent consensus around SegWit2X.

The Bitcoin Cash supporters:

Jihan Wu, co-founder of Bitmain, said his company, which has a large percentage of the network's hash power, would begin mining BCC as early as August 1, 12 hours and 20 minutes after the start of the UASF .

Jiang Zhuoer, founder of BTC.TOP , said his company would undermine BCC if it is economically incentivized to do so.

The exchange platform ViaBTC , which already offers futures on the price of the BCC, also announced the creation of a mining pool dedicated to Bitcoin Cash.

Bitcoin ABC - technical specifications (in short):

For the chain to split in two, a block larger than 1 MB must be mined, the fork block.

{C}     The low limit of acceptance of the blocks will be 2 MB, and the upper limit of 8 MB.

{C}     There will also be a soft fork  limiting signing operations to 20,000 per transaction.

{C}     The size of the blocks submitted by minors will not be determined by the code but by the economic incentive (minors will be punished if they submit too large blocks).

{C}     The channel will be protected against replay attacks .

{C}     SegWit will not be implemented in the first time.

The channel had to be mined privately by Bitmain for 72 hours minimum, and the blocks released on the network if the circumstances dictated it. The list of conditions (non-exhaustive) was as follows:

{C}     Chain-split between legacy chain and chain 148,

{C}     Strong feeling of the market in favor of a hard fork increasing the size of the blocks.

{C}     In the case where another hard fork increasing the size of the blocks was a great success (Bitcoin Unlimited or Bitcoin XT for example), Bitmain would undermine the channel and abandon its private channel to cancel the risks associated with its reorganization.

bitcoin abc fork