Uncle Mining, an Ethereum Consensus Protocol Flaw

A year ago I was hired by Eth Dev Ltd through Coinspect to perform a security audit on the Ethereum design. One of our findings was that the uncle reward strategy in Ethereum was weird, and could lead to miners abusing the uncle rewards to almost triple the money supply. We discovered this problem because […]

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“SPV mining” is the solution, not the problem

Is was Wednesday, March 26, 2014. It was a cold winter outside, but not inside an old building of the Princeton university campus. The room, full of people, was warm. I was standing in front of some of the brightest minds in Bitcoin: Andresen, Bonneau, Eyal, Maxwell, Miller, Gün Sirer, Szabo, Todd and Zooko, to name only a few. My talk was about “SPV Mining”, […]

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Proof of unique blockchain storage revised

In this post I describe a new way to for a node in the Bitcoin blockchain to prove to its peers that it is storing a copy of the blockchain. The core primitive that enables this protocol this is the Asymmetric-Time Function (ATF). You won’t get much info by googling ATF since I coined that term […]

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DagCoin: a cryptocurrency without blocks

Back in 2012 I thought a lot on a new cryptocurrency that could merge the concepts of transaction and block. Each transaction would carry a proof-of-work and reference one or more previous transactions. The resulting authenticated data structure would be a Direct Acyclic Graph (DAG) of transactions where each transaction “confirms” one or more previous […]

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How DECOR++ can eradicate selfish mining incentive by design

A year ago I proposed the DECOR protocol, a new rule for cryptocurrencies to reduce significantly the amount of orphan blocks and then allow block rate to be as high as one every 5 seconds, and at the same time it promised to address the problem of selfish mining. After one year, I’ve received very […]

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Simulated Brains, Smart-contracts and the direction of time

There are three fantastic discoveries in computer science that fascinate me: fully-homomorphic encryption , Indistinguishability Obfuscation, and  sz-Snarks. Using these constructions, it’s possible to create an obfuscated program and allow others to execute the program in a way that the when the program produces an output, people cannot learn anything about its inner workings. The […]

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Faster SHA-256 ASICs using carry reduced adders

The core part of Bitcoin mining is performing a double SHA-256 hash digest and comparing the result against the target. Two years ago, in 2013, the first Bitcoin ASIC miners appeared on the market. Since then, mining ASIC technology advanced both in terms of the manufacturing technology (the node) and in terms of design, to […]

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