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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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Proof of unique blockchain storage

One of the key elements to measure the health of a blockchain based cryptocurrency is the number of nodes actually storing the blockchain. The blockchain grows normally according to the number of payments per second. But as a cryptocurrency becomes popular, the number of payments per second increases, and the blockchain growth rate also increases. […]


The Bitcoin Freeze on Transaction Attack (FRONT)

Two month passed since my last post and the reason is I’ve been terribly busy working for Coinspect and also helping with Bitcoin Core security. A rainy Sunday evening is a great moment to write, so here is my new post, with some new thoughts. People are trying to understand the security guarantees Bitcoin provides. […]

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Blockpad: Improved Proof-of-work function with decentralization incentives

A few posts ago I presented BlockPow, an example of a proof of work function that practically reduces the incentives for users to join mining pools. The shorter the block interval, the best it works. Let’s first summarize the idea behind BlockPow:  if a miner tries to join a pool, then he incur in overhead […]

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Preventing Geographical Centralization of Cryptocurrency Mining with the LIMIO protocol

There has been much discussion recently about how to prevent mining pools. There are theoretical and practical approaches. Nevertheless preventing mining pools is not the same as preventing geographical centralization. Mining pools incentives are: Reduce payoff variance. Reduce resource usage. Normally Bitcoin node would require more resources (memory,disk, bandwidth) than a pooled miner. Reduce exposition to […]

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Preview of Identiva PassKey: vote for us for the Cisco IoT Challenge

A friend of mine and me have developed a new technology and device that we think can be a game changer in web authentication. I’d like you take a look and vote for as for the Cisco IoT Challenge (you must register first to vote….#?@!) We’re launching a new company (Identiva Security) to develop the […]

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July 2009 Mystery Solved

A year ago I analyzed a mining pattern that suggested a correlation between Satoshi computer and another computer mining at the same time. This relation had been highlighted to me by a another user in the forums (I don’t remember who) . From this correlation I conjectured that the same computer was mining both patterns […]

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