1,088 research outputs found
Majority is not Enough: Bitcoin Mining is Vulnerable
The Bitcoin cryptocurrency records its transactions in a public log called
the blockchain. Its security rests critically on the distributed protocol that
maintains the blockchain, run by participants called miners. Conventional
wisdom asserts that the protocol is incentive-compatible and secure against
colluding minority groups, i.e., it incentivizes miners to follow the protocol
as prescribed.
We show that the Bitcoin protocol is not incentive-compatible. We present an
attack with which colluding miners obtain a revenue larger than their fair
share. This attack can have significant consequences for Bitcoin: Rational
miners will prefer to join the selfish miners, and the colluding group will
increase in size until it becomes a majority. At this point, the Bitcoin system
ceases to be a decentralized currency.
Selfish mining is feasible for any group size of colluding miners. We propose
a practical modification to the Bitcoin protocol that protects against selfish
mining pools that command less than 1/4 of the resources. This threshold is
lower than the wrongly assumed 1/2 bound, but better than the current reality
where a group of any size can compromise the system
A Deep Dive into Blockchain Selfish Mining
This paper studies a fundamental problem regarding the security of blockchain
on how the existence of multiple misbehaving pools influences the profitability
of selfish mining. Each selfish miner maintains a private chain and makes it
public opportunistically for the purpose of acquiring more rewards
incommensurate to his Hashrate. We establish a novel Markov chain model to
characterize all the state transitions of public and private chains. The
minimum requirement of Hashrate together with the minimum delay of being
profitable is derived in close-form. The former reduces to 21.48% with the
symmetric selfish miners, while their competition with asymmetric Hashrates
puts forward a higher requirement of the profitable threshold. The profitable
delay increases with the decrease of the Hashrate of selfish miners, making the
mining pools more cautious on performing selfish mining.Comment: 6 pages, 13 figure
Impact of Geo-distribution and Mining Pools on Blockchains: A Study of Ethereum
Given the large adoption and economical impact of permissionless blockchains,
the complexity of the underlying systems and the adversarial environment in
which they operate, it is fundamental to properly study and understand the
emergent behavior and properties of these systems. We describe our experience
on a detailed, one-month study of the Ethereum network from several
geographically dispersed observation points. We leverage multiple geographic
vantage points to assess the key pillars of Ethereum, namely geographical
dispersion, network efficiency, blockchain efficiency and security, and the
impact of mining pools. Among other new findings, we identify previously
undocumented forms of selfish behavior and show that the prevalence of powerful
mining pools exacerbates the geographical impact on block propagation delays.
Furthermore, we provide a set of open measurement and processing tools, as well
as the data set of the collected measurements, in order to promote further
research on understanding permissionless blockchains.Comment: To appear in 50th IEEE/IFIP International Conference on Dependable
Systems and Networks (DSN), 202
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