Multi-mode Cryptocurrency Systems

In the past years, the security of Bitcoin-like protocols has been intensively studied. However, previous investigations are mainly focused on the single-mode version of Bitcoin protocol, where the protocol is running among full nodes (miners). In this paper we initiate the study of multi-mode cryptocurrency protocols. We generalize the recent framework by Garay et al (Eurocrypt 2015) with new security de nitions that capture the security of realistic cryptocurrency systems. e.g. Bitcoin with full and lightweight nodes. As an immediate application of our new framework, we analyze the security of existing blockchain pruning proposals for Bitcoin and Ethereum aiming to improve the storage e ciency of network nodes by pruning unnecessary information from the ledger.