Resisting newborn attacks via shared Proof-of-Space

Abstract

In the cryptocurrency literature, Proof-of-Space has been a potential alternative for permissionless distributed consensus protocols not only due to its recyclable nature but also the potential to support multiple chains simultaneously. Namely, the same storage resource can be contributed to the consensus of more than one chain. However, a direct shared proof of the same storage brings about newborn attacks on new chain launching since holders of a substantial amount of resources can easily devastate a new chain with minor underlying storage at almost no cost, deviating from the decentralized principle of cryptocurrencies. To fix this gap, we propose an innovative framework of single-chain Proof-of-Space and further present a novel multi-chain scheme which resists newborn attacks effectively by elaborately combining shared proof and chain-specific proof of storage. Our framework covers both classical Nakamoto consensus (with one leader per round) and hybrid consensus (with multiple leaders per round). Specific protocols for both cases are presented. A committee-based consensus is leveraged to realize the multiple leader case. We show that both consensus schemes have realized our desired functionality without compromising consistency or liveness.