BIP91 is likely to be activated. What's next? What is it? What is BIP141(segwit) and BIP148 (uasf)?

ktoosiu (43)in #bitcoin • 7 years ago (edited)

BIP91 Currently has more than needed hash power and it's likeli to be confirmed within next 50 block (about 2 GMT). But What will it change? What's next steps to activate a segwit?

BIP141, BIP148, BIP91

BIP141 - segwit

This BIP (bitcoin improvement proposal) defines a new structure called a "witness" that is committed to blocks separately from the transaction merkle tree. This structure contains data required to check transaction validity but not required to determine transaction effects. In particular, scripts and signatures are moved into this new structure. Also provide several other changes.
It's a soft fork, to activate it we need super majority of a hash power - 95% mined block in 2016 blocks period needs to signal this bip to lock it, then after another 2016 blocks when miners can prepare segwit will be activated.

BIP148 - UASF

UASF - User Activated Soft Fork
Due to big miner pool disagree original segwit deployment is really hard to implement.
BIP148 is a way to use a nodes to omit miners vote power to activate Segwit.
UASF bitcoin nodes after 01.08 will reject and ban all blocks that don't signall BIP141 (Segwit), so blockchain will be fulfiled only by segwit-ready blocks which will lead to normal BIP141 activation (95% in 2016 blocks). However depends on number of uasf nodes it may lead to chain split (i.e. BTC ABC that would accept rejected blocks and split to second blockchain) and miners lose of money.

What is BIP91?

It's an segwit activation method made to avoid chain split. This needs an 80% signalling blocks in a period of 336 blocks (2.5 days). When BIP91 will be locked all miners have a one more period to prepare, then all non-segwit signalling blocks will be rejected what will lead to normal BIP141 activation (95% in 2016 blocks).

So what will happen now?

If BIP91 will be locked miners will have 336 blocks to prepare (2.5 days) and then all the blocks need to signall segwit-ready otherwise they will be rejected. All the blocks will be signalling so since next period (about ~7 days from now) will start a segwit activation period (95% will be reached due to bip91 and bip148 non-segwit block rejecting), when period will end after 2016 block (2 weeks) segwit will be locked, and after another 2 weeks - about end of september we will be able to use segwit!