Category: Bitcoin

On Fees

When sending less than €1,000 of Bitcoin it’s worth paying attention to fees, but keep mind that your payment is competing with transactions that move €100,000 on equal terms. Transactions are charged per byte, not as a percentage of the amount. But willingness to pay is obviously a percentage of the amount.

It’s interesting to note that although the price has increased more than 10x over the past year, transaction amounts in BTC terms haven’t changed much:

Neither have fees as a percentage, they still hover around 0.75%:

I was trying to improve the functional tests for bumpfee, a Bitcoin Core wallet feature that lets you increase the fee of a transaction that’s unconfirmed and stuck. Unfortunately I introduced a bug in the test, which I’m still in the process of tracking down. Every disadvantage has its advantage, so I took the opportunity to better understand the functional test framework and its powerful debugging tools.

A Short History of Replay Protection

This article is based on the slides I used for a presentation at the Hong Kong Bitcoin Developer meetup on November 1st, plus some feedback I received on the chainspl.it Slack. This was before SegWit2x was called off, but in the interest of (my) time, I haven’t adjusted this article to reflect that. I’m sure something similar will happen again anyway and it’s a good mental exercise to think through what could have happened.

Investor TL&DR

For non-technical readers a useful perspective — even if technically not accurate — is to distinguish between airdrops and contentious hard forks. This assumes you are in possession of your private keys, as you should.

Opt-in hard-fork without alternate transaction history?

IETF’s RFC 7282 is an eloquent document which describes important aspects on koop consensus, and worthwhile if you want a more nuanced interpretation than “widespread agreement and disagreements addressed (even if not acommodated)”.

Measuring Consensus

Once we have a concrete technical proposal, and it seems to have some traction, we need to figure out if we really have consensus before it gets deployed.

Moving from RFC 7282 style technical rough consensus to economical and political (rough) consensus is quite problematic. If you want to stay in the spirit of RFC 7282 then you should only use polls to see if there is any opposition. You then need to actively go out and figure out what people’s concerns are and make sure those are reasonably addressed. You have to go through all that before you accept anything below 100% support.

Replay Protection in The Blockchain Wars

First, I’ll let Jimmy Song explain transaction replay attacks:

However what this short video doesn’t cover, is that there are multiple levels of replay protection. I believe a lot of anger and confusion stems from not properly understanding this. So I’ll do my best to explain.

Historical Bitcoin Core Client Performance

After reading about performance optimizations on the Bitcoin Core blog, I wanted to see a chart of that. I couldn’t find one, so I spun up a bunch of EC2 nodes and set out to measure how long it took each new version of the bitcoin core client to sync the full blockchain.