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Bitcoin: The other environment argument

During the last few weeks, a lot of discussion has been going on about Bitcoin’s energy consumption and how it relates to the fiat system’s energy consumption. I’ve read a few articles about it and some are really good. I added some links at the end...

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New book, Grokking Bitcoin

I’ve been very silent on this blog lately. Sorry about that! The reason is that I’m working hard on a new book, Grokking Bitcoin. The book will be published on Manning Publications during spring 2018. This book is a very technical book, intended primarily...

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Steal sidechained coins

This is a follow-up post on my series on sidechains. I recommend reading SPV proofs and reorg proofs in sidechains and Compact SPV proofs in order to understand this post. But if you’re already familiar with sidechains, just go ahead! There is a risk that miners...

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Atomic swaps

This is a follow-up on my SPV proofs and compact SPV proofs posts. While SPV proofs are interesting and the only way to move funds from one chain to another, moving funds takes time. Typically it would take on the order of days to complete a transfer between chains....

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Compact SPV proofs

My last blog post was about sidechains and how SPV proofs and reorg proofs were the key ingredients for transferring funds from one chain to another. In this post I will talk about “compact SPV proofs”. As usual, I’m writing to educate myself, and...

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SPV proofs and reorg proofs in sidechains

I’ve been reading the sidechains paper, and I find it really fascinating. There are a few things that I had a hard time understanding in this paper, and the Internet fell short on explaining. Therefore I’m writing this blog post to educate myself and...

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Weak Blocks – The Good And The Bad

I’ve been looking at weak blocks and I’m trying to sort out the good and the bad about it. How it works Weak blocks are blocks that does not appear in the blockchain, only in the p2p network. Miners produce these blocks with reduced difficulty, for example...

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Proof of Payment design choices

In this post I’ll try to explain some design choices for BIP 120, Proof of Payment, and also comment on some critique against it. Basically a Proof of Payment looks exactly like a Bitcoin transaction: Note how Pop(T) in indistiguashable from a Bitcoin...

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Sorting out Replace By Fee

Recent months, I’ve been pretty confused over all the different flavors of Replace By Fee (RBF). There’s RBF, FSS-RBF, RBF scorched earth, opt-in RBF and possibly heaps of other variants. This blog post aims at bringing clarity (to me) what all this means...

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Kalle Rosenbaum

Please drop me a line at, or @kallerosenbaum on Twitter.