Stability and Scalability of Blockchain Systems

摘要

The blockchain paradigm, introduced in the Bitcoin whitepaper [10], enables distributed consensus over a peer-to-peer network. Each peer constantly mines new information called blocks. Thus, blocks in the network are created over time. Each peer that creates (mines) a block also creates references to one or more previously created blocks. Peers also communicate blocks in order to synchronize their information sets; i.e., the sets of blocks and references the peers are aware of. One of the main goals of a blockchain system is to enable consensus through distributed trust. Trust is achieved by the references - a peer only references a block for which they have verified the contents. In order to achieve distributed consensus, all peers should trust the same blocks. If all peers trust a block, it is called confirmed. A natural performance requirement of a blockchain system is that the subset of blocks which are confirmed grows with time as blocks are created This, however, is not guaranteed as blocks are created over time at different locations in the network and then need to be disseminated. Due to bandwidth limitations, communications on the network are not instantaneous and experience delays. If blocks are created too quickly [1, 5,14], the delays cause network congestion and can prevent a blockchain system from confirming blocks. As blockchain technology matures and evolves [1, 3, 5, 10,12-14], it is natural to study the scalability challenges that arise due to its adoption.