37 Days to SegWit: When SegWit is Live…

Ever since SegWit was first introduced at Scaling Bitcoin Hong Kong in 2015, I have found myself starting sentences with, “When SegWit is live…”, followed by some prediction about how this technology will supercharge bitcoin. In the spirit of the optimism around growing support for SegWit among miners and the broader bitcoin economy, I thought I’d share some of the things I’m excited about for “when SegWit is live” on bitcoin in 37 days (or less!).

When SegWit is live…

  • More transactions will fit in each block, and as far as I can tell this will not come at the expense of node or hashpower decentralization. In my humble opinion, more transactions per block is always a good thing as long as we don’t sacrifice the security of the system.
  • Transaction malleability will be fixed for SegWit transactions, enabling advanced scaling technology such as a more secure version of the Lightning Network. Lightning Network is very exciting because it opens up whole new micropayment-related use-cases that have simply not been possible on-chain.
  • It will be safer to increase the block size limit, due to the way that SegWit fixes the quadratic scaling of hashed data problem. As mentioned earlier in this post, more transactions per block is a good thing so long as bitcoin’s security is not compromised.

I’m very excited to see these and other benefits added to bitcoin because taken together, they strongly reenforce bitcoin’s leadership in the cryptocurrency market since virtually any cryptocurrency feature or use-case someone could think of will be possible either on bitcoin’s “mainchain” or a Layer 2 protocol such as sidechains or Lightning. This adds a tremendous amount of utility for the millions of people using bitcoin, and further increases the network effect and security that makes bitcoin such a powerful technology.

To the moon!

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46 Days to SegWit: Growing Consensus in the Bitcoin Economy

You can read previous posts in this series here and here. You can find my guide about how to enforce the BIP148 UASF with your Electrum bitcoin wallet here. For templates that you can use to fill-in-the-blank and request that your favorite economic nodes and mining pools support the BIP148 UASF, scroll to the bottom of this post.

A lot has happened since last week’s blog post about the BIP148 UASF. Bitmain, the largest ASIC miner manufacturer, released their “contingency plan” for a “User Activated Hard Fork” in case the BIP148 UASF activates before the Segwit2x soft fork. The way I read this is that Bitmain is willing to do whatever it takes to avoid activating SegWit, which is quite surprising given that less than a month ago they signed the Segwit2x agreement to activate SegWit. If Bitmain would just signal for SegWit via BIP141 now, that would go a long way towards preventing a chain split on August 1. But I digress.

In more positive news, bitcoin developer James Hilliard submitted a pull request to the Segwit2x GitHub repository yesterday with code that attempts to make the Segwit2x deployment compatible with BIP148. While it’s not as good a solution as it would have been to make the proposal compatible from the start, this is likely the next best thing at this juncture. For that, I thank James for making the effort.

Continuing the theme of support for SegWit and BIP148, several important economic nodes have recently announced their support, undoubtedly thanks to the many supporters who have voiced their preference in public and private messages. These economic nodes include Ledger, a hardware wallet manufacturer, and the team behind Bitsquare, a decentralized exchange application. You can learn more about the growing support for SegWit and BIP148 among developers and economic nodes on this page of the bitcoin wiki.

If you support the BIP148 UASF, you should contact the folks behind your favorite wallets and exchanges if you haven’t already and ask them to enforce the BIP148 UASF. You can find fill-in-the-blank templates to do this at the bottom of the post here.

Since last week’s blog post I was also invited onto three different YouTube shows to discuss SegWit and the BIP148 UASF. You can watch these episodes below:

Hungarian Crypto Show


This Week in Bitcoin


Bitcoin News #42


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My thoughts on scaling bitcoin

This is a somewhat long post, so I’ll give you the opportunity now to save yourself some reading time. Most of the post is historical context. If you are familiar with the history of bitcoin’s scaling debate, or are otherwise uninterested in my take on it, you can skip to the section at the end called “My conclusion”. If you’re like “damnit John just get to the point,” read the TL;DR at the bottom and you can read the rest of the post to fill in the details later.

I have been following the discussion around how to scale bitcoin since I first started researching the technology. I knew then as I do now that this will be the “make or break” debate for bitcoin, and also the most contentious given the challenges involved. I just did not know then how contentious it would be. Rather than solve the problem through hard forks or whatever other means necessary while bitcoin was small and relatively malleable, bitcoin grew very big, very fast, and the can has been repeatedly kicked down the road by developers and users to the point we are at today.

Even though it was obvious years ago that the only way bitcoin would reach global scale is through the widespread use of off-chain transactions, the systems needed to support such usage have only recently begun to be developed and none of any significance have yet been released in production. Thankfully, some forward-looking companies and bitcoin developers have been making the necessary investments to support such systems, including the Lightning Network and sidechains. Unfortunately, these systems are not ready yet, and the altcoins that have been nipping at bitcoin’s heel are now gnawing off its foot. There’s still a chance to save the rest of bitcoin and mend the wounds, but decisive action is needed, stat.

When I first gained an understanding of the issues at play in scaling bitcoin – mainly the effects on hashpower and full node centralization – I imagined that the off-chain technologies required to scale bitcoin would be ready by the time bitcoin hit its stride and gained mainstream adoption. I envisioned that there would be a graceful transition from on-chain to off-chain networks for daily “retail” usage. Not only has the transition not happened yet, when it does happen, it will hardly be considered “graceful”.

Due to various factors, bitcoin has gained a lot of attention recently. This has led to increased usage, and, subsequently, higher per-transaction fees. The average transaction fee today is about $1.00 USD. Just a year ago, it was less than $0.15. I am not opposed to high on-chain fees – in fact, I expect them to be at least 10x-20x higher or more in the future, and am completely ok with that. What I am opposed to is all bitcoin transactions being priced that high. Currently, users have no safe alternative if they want to transact in bitcoin. Either they swap IOUs on some trusted third party’s centralized database, or they pay $1.00 or more for every on-chain transaction. This isn’t the way it’s supposed to be.

Many of the decentralized “layer 2” off-chain solutions that have been proposed require slight modifications to bitcoin’s base “layer 1” protocol to work securely. One of the proposed modifications is called Segregated Witness (SegWit). While it’s not a scaling silver bullet, it paves the way for some exciting changes to bitcoin that will provide significant advancements for on-chain and off-chain scaling. Segregated Witness is not the only such proposal, but it is the one that has received the most attention and testing. And most importantly, it is production-ready today.

Despite a prior agreement to support SegWit, a large contingent of miners have failed to give it the support it needs to be activated on the main bitcoin network. The exact reasons that outspoken miners have given for their refusal to support SegWit activation vary, but the most common reason is that they won’t support SegWit unless a hard fork “non-witness” block size increase is bundled with it.

For various reasons, including concerns about the length of time it would take to test and safely deploy a hard fork, bitcoin developers have been unwilling to release a version of Bitcoin Core that would hard fork the network. They have presented several hard fork proposals for peer review, but none have yet gained the support required to merit merging into Bitcoin Core.

And so we have a stalemate.

My conclusion

After reviewing the arguments on all sides, and investigating nearly every scaling proposal put forward for public review, I have come to the conclusion that the miners should run SegWit software and signal for activation immediately, followed by a user-activated soft fork led by the economic majority when sufficient miner support is reached. Since signaling can be faked, a UASF will expose anyone who is swimming naked when the tide goes out (see: BIP66 fiasco).

If current holdout miners do not signal their support for SegWit, then the economic majority should still do a UASF, because the miners will quickly change their mind anyways (or else risk losing a lot of money). If the miners attempt to attack the UASF chain, then I will advocate for a transition away from double-SHA256 Proof of Work.

As stated earlier in this post, SegWit is the only proposal that has been rigorously examined and tested and put into production use by miners and full nodes. SegWit is being used in production by multiple altcoins, and to date there have been no bad incidents attributed to its deployment on these networks.

Additionally, SegWit does not preclude other on-chain scaling proposals, including non-witness block size increases. Given the nature of the anyone-can-spend hack, yes, we would (probably?) be locked into SegWit for the foreseeable future, but we can still layer other solutions on top – and there are a lot of great proposals that I would love to see tested and, if given a high safety rating, implemented in the future.

I have read and understand (to the extent possible given that I am not a software engineer) most of the reasons for opposing SegWit. Based on what I have read, heard, and have been told by engineers that I trust, the benefits of SegWit outweigh the costs. The developers that have spent time adding support for SegWit to their wallet and node software seem to agree. No other scaling proposal has such widespread support.

What’s important to understand is that SegWit is production-ready today, and any modification to include a hard fork or any other significant changes would simply delay scaling even further due to the time needed for testing and deployment. A hard fork requires an ecosystem-wide upgrade to go into effect, which takes time. A soft fork only requires miner support, and the SegWit soft fork is ready for activation today. We need scaling now, not in another six-to-twelve months.


Activate SegWit on bitcoin as soon as possible. Investigate other scaling solutions in parallel and implement the best of those later.


I realize that the debate has evolved from “what is the best way to scale bitcoin?” to “should Bitcoin Core continue to be the ‘reference implementation’ of the bitcoin protocol?” That question is outside the scope of this post and may be addressed in a future post. In any case, activating SegWit and changing the reference implementation are orthogonal issues; neither precludes the other.

Relevant links

Scaling Bitcoin series [link]

On Chain Scaling series [link]

Segregated Witness information [link]

ViaBTC: Why We Don’t Support SegWit [link]

Bitcoin miner: Why We Must Oppose Core’s SegWit Soft Fork [link]

Bitmain: Regarding Recent Allegations and Smear Campaigns [link]

Bitcoin Hard Fork Research [link]

Bitcoin Roundtable Consensus [link]

User-Activated Soft Fork (UASF) information [link]

BIP66 fork information [link]

A summary of the opposition to SegWit [link]

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