Bitcoin’s Independence day – August 1 to activate SegWit by UASF

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  • Short explanation on what UASF and BIP148 are, down below for the article!
What is a UASF?

UASF stands for User Activated Soft Fork. It’s a mechanism where the activation time of a soft fork occurs on a specified date enforced by full nodes, a concept sometimes referred to as the economic majority. A UASF requires a lot of industry support and coordination, which is good practice for eventual hard forks which requires even more industry coordination. In the past, a UASF was successfully carried out to activate the P2SH soft fork (BIP16). The UASF concept was combined with SegWit activation in the BIP148 proposal which can be found here:

What is BIP148?

BIP148 is a UASF that is designed to cause the existing SegWit MASF deployment to cause activation in all existing SegWit capable node software (which currently is 80% of the network nodes). How does BIP148 Work? From August 1st, 2017, miners are required to signal readiness for SegWit by creating blocks with the version bit 1. This will cause all SegWit ready nodes, which make up over 80% of the network, to activate and begin enforcement. Link for reference: Miners must also check blocks prior to their own and ensure that they also signal for SegWit, and only build on those blocks.

By Nicolas Dorier [Btc Developer] –

I am a big fan of the approach of Bitcoin Core to adopt minimally disruptive update to the protocol. And as I already said, I am against BIP148 based on this value.

Nevertheless, a good part of the community seems to support it, and as a service provider with QBitNinja, as a consultant and maintainer of Bitcoin projects of my customers, I have a duty to understand how decision of the community impact what I built.

I would have preferred status quo than today’s situation, but on another side, I don’t see how it could have been avoided. I can’t either ignore it, and I want to show you why.

Here is the decision tree of what can happen after BIP148.


  • Node operator

There is only one difference as far as the node operator is concerned.
As a non-BIP148 node, during Post-Split you will face one of the following painful situation.

  1. A permanent chain split, where your chain keep the majority hash power.
  2. Chain will be wiped out after several confirmation.
  3. As a BIP148 node, you face only one risk
  4. Ending up on the minority chain.

If BIP148 chain ever become a majority chain, then a big reorg will happen for the non-BIP148 nodes.

  • Industry player

As you can see, your decision does not matter Pre-Split. Pre-Split result is only decided by Miners.

In the event of a split, then, if miners do not revert their decision, you will have to step in and decide whether you decide to create a big reorg OR trying to keep two chains.

Keeping two chains is impossible to assure in the long term. If Miners change their minds due to difference of profitability between the two chains, then a reorg will happen, hurting non-BIP148 users.

For this reason I think that QBitNinja, my internal projects and those of my customers will run BIP148 nodes. I am still deeply thinking about that, but in the event of a split, then the least disruptive solution is to run BIP148.

As additional measure, I will advise customers, to stop using Bitcoin until Segwit activates for non-BIP148 (the big reorg happened), or if it is clear that BIP148 will never catch up the main chain.
This can reasonably happen if Core decide to explicitely invalidate the first block after fork of the BIP148 chain on the base of minimal disruption, if the BIP148 chain takes too long time to catchup the main chain. This scenario would split bitcoin permanently.

  • As a Miner

Without your support, this update will likely hurt non-BIP148 node.

  • As a User

Do not use Bitcoin from august until the situation get cleared.

  • Conclusion

BIP148 might well be the end of the discussion. In summary, if you are a node operator or a industry player, you should support BIP148 whether you agree with it or not, given that you value minimal disruption post Split, and want to protect yourself against a devastating reorg, and that you consider Segwit a sane proposal.

I personally think that BIP148 will work. I would have preferred status quo, but the safest way for my services is to update to BIP148. This is what I will advise to other service providers, and users.

Note that this is what will happen, whether or not the NYC agreement materialize, and whether or not consensus alternative like BIP149 is reached. There is no workaround but to face what is coming.

BIP148 will rock the boat. Welcome in Bitcoin. By @nicolasdorier