Posts Tagged Bitcoin

A Bitcoin transaction that takes 5 hours to verify

In 2013 I found a Bitcoin transaction that takes 3 minutes to verify (CVE-2013-2292) related to O(N^2) hashing in signatures. Since then, the O(N^2) argument has popped up in many contexts, mainly in discussions about a block size increase. Now the problem is partially solved by Segwit. During January 2016 I tried to beat the […]

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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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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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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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July 2009 mistery 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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