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. […]

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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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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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How you will not uncover Satoshi

Computer forensics is the science of finding evidence in computers and digital documents, and when a hacker perform forensics, better be prepared for the unknown. Satoshi did many things in order to try to stay anonymous: he used Tor, he used anonymous e-mail servers, he did not disclose personal information in posts and probably he […]

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Theoretical and Practical Nonoutsourceable Puzzles

The fact that GHash.io has reached twice 51% of the Bitcoin hashing power this year has pushed scientist and alt-coin creators to find for other proof-of-work puzzles that discourage mining coalitions. Several months ago I read the foundations of Nonoutsourceable Puzzles as proposed by Andrew Miller, and now his paper (working with Elaine Shi, Jonathan […]

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Deterministic Signatures, Subliminal channels and Hardware wallets

A subliminal channel in a signature scheme allows a signing party to send a covert message to an authorized receiver of signed messages without anyone else noticing it. One property of ECDSA, DSA and many similar digital signature schemes (such as Schnorr) is that they need to produce, for each signature generation, a fresh random […]

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