On the Sustainability of Bitcoin Partitioning Attacks

A series of recent studies have shown that permissionless blockchain peer-to-peer networks can be partitioned at low cost (e.g., only a few thousand bots are needed), stealthily (e.g., no control plane detection is available), or at scale (e.g., the entire bitcoin network can be divided into two). In this paper, we focus on the sustainability of partitioning attacks in Bitcoin, which is barely discussed in the literature. Existing studies investigate new partitioning attack strategies extensively but not how long the partition they create lasts. Our findings show that, fortunately for Bitcoin, the permissionless peer-to-peer network can be partitioned but only for a short time. In particular, two recent partitioning attacks (i.e., Erebus [12], SyncAttack [10]) do not maintain partitions for more than 10 min in most cases. After analyzing Bitcoin's peer eviction mechanism (which makes the two original attacks difficult to sustain), we propose optimization strategies for the two attacks and calculate the total cost of the optimized attacks for a 1-hour attack duration. Our results complement the original attack studies: (i) the optimized Erebus attack shows that it requires at least one adversary-controlled Bitcoin node close to a target and a few additional expensive attack steps for sustainable attacks, and (ii) the optimized SyncAttack can create sustainable partitions only with excessive cost.