Decentralized Systems Security Lab

Bad news first: It turns out that the security of hash time lock smart contracts (HTLC) relies on the good intentions of blockchain miners, or at least their short-sightedness. That’s right, it is based on the assumption that miners, those businesses that make money from energy, are altruistically naive. [Read More]

Proof of Work (PoW) Blockchains implement a form of State Machine Replication (SMR). Unlike classical SMR protocols, they are open, i.e., anyone can join the system, and the system incentivizes participants, called miners, to follow the protocol. Therefore, unlike classical SMR protocols, reasoning about blockchain security relies not only on bounding the number of malicious participants. One should crucially ask whether miners are indeed incentivized to follow the prescribed protocol. This is the topic of this post. [Read More on Decentralized Thoughts]

TL;DR We have discovered a denial-of-service attack on Bitcoin-like blockchains that is much cheaper than previously described attacks. Such blockchains rely on incentives to provide security. We show how an attacker can disrupt those incentives to cause rational miners to stop mining. Technical report here. Original blog post here. [Read More]

High power consumption is critical to the security of many cryptocurrencies: to compromise them an attacker would need to spend as much power as the rest of the system combined. And this mechanism works: major cryptocurrencies have demonstrated unprecedented resilience, despite no lack of incentive to violate their security and steal money. But is the security threshold not exaggerated? Why is power consumption at the rate of Austria the right amount? Maybe half of that is sufficient? Or a quarter? Arguably, the adverse ecological effects of superfluous expenditure imply that we should target a lower expenditure rate, to achieve Just... [Read More on Medium]