Multi-mode cryptocurrency systems

Alex Chepurnoy (http://ergoplatform.org/team.html) from Ergo and IOHK Research will present his recent work about blockchain pruning (joint work with Tuyet Duong and Hong-Sheng Zhou).

#################

Bitcoin is a decentralized digital cash system on top of a distributed, append-only public ledger. Bitcoin transactions are recorded in the public ledger, and the ledger is maintained by a network of nodes via proof-of-work mechanism. Among these network nodes, some are in ``full mode'', and the remaining are in certain ``light'' modes. Each full-mode node records the complete history of transactions, which allows the node to verify the validity of new transactions by itself. The nodes in a light mode may only store a partial history of transactions, or a succinct version of the history; this allows the Bitcoin protocol to be executed in computing devices where storage is limited.

In the past years, the security of Bitcoin-like protocols has been intensively studied. However, previous investigations are mainly focused on the {\em single-mode} version of Bitcoin protocols, i.e., the protocol running among full-mode nodes.

In this talk, we will introduce our recent original study of multi-mode cryptocurrency protocols. We generalize the recent framework by Garay et al (Eurocrypt 2015) so that the security of a larger class of protocols can be analyzed. 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 efficiency of network nodes by pruning unnecessary information from the ledger.