Decentralized Systems Security Lab

Selfish mining is a known security vulnerability in blockchain protocols. In our latest paper, we show reward variability leads to increased vulnerability to selfish mining in Bitcoin and similar cryptocurrencies. To do so, we use deep reinforcement learning to analyze the effect of whale transactions, occasional large rewards, on selfish mining. Since reward variability in Bitcoin will increase in the future, its security will degrade. [Read More on Medium]

Nakamoto’s consensus protocol works in a permissionless model, where nodes can join and leave without notice. However, it guarantees agreement only probabilistically. Is this weaker guarantee a necessary concession to the severe demands of supporting a permissionless model? [Read More on Decentralized Thoughts]

The Selfish mining attack against blockchain protocols was discovered and formalized in 2013 by Eyal and Sirer (also see our blog post). The Bitcoin community has mentioned similar types of attacks in 2010. This attack remains a vulnerability of all operational blockchains we are aware of. For Bitcoin’s blockchain algorithm (under reasonable network assumptions), a coalition controlling over 1/4 of the mining power can improve its revenue using this attack. The situation is even worse if we consider more powerful attacks (see Sapirshtein, Sompolinsky, Zohar, Heilman et al., and Nakak et al.). [Read More on Decentralized Thoughts]

Prominent smart contracts, e.g., roll-ups, critically rely on timely confirmations of their transactions. Sadly, that’s not how blockchain works, as confirmation times depend on transactions fees, where the required fee is determined by the volatile fee market. We present LedgerHedger, the first smart contract that facilitates a reservation for a future transaction confirmation. LedgerHedger is secure, incentive-compatible, and has low overhead for practical future-transaction parameters. [Read More]

Securing digital assets like cryptocurrencies and NFTs is a tricky business, as demonstrated by numerous losses and heists. The challenge of storing digital assets applies equally to individuals and to larger actors - from companies to cryptocurrency exchanges to the largest financial services corporates. [Read More]