Fairness in block-chain systems

Speaker : Sara Tucci
Date: 10/07/2017
Time: 2:00 pm - 2:30 pm
Location: LINCS Seminars room


Abstract: Formal security analyses for block-chains derived the famous
“honest majority” assumption: the system well-behaves only if the
majority of the hashing power is in the hands of honest miners. This
result has been proven without taking into consideration economic
aspects related to miner’s incentives and their rational behavior.
Other works analyzed selfish mining with respect to incentives and
concluded that the majority assumption is not enough under certain
conditions. All these studies make the implicit assumption that the
health of the system is only in the hands of miners, but what about if
all the users leave the system. Since the system is composed of miners
and users and since these two sets are disjoint in practice, block
chain’s health strictly relates to the capacity of promoting honest
participation both for miners and users. In this talk we explore the
relationship between participation and the notion of fairness. In
general terms, fairness can be defined as the overall satisfaction of
justified expectations of the participants. If a block-chain system is
fair, then its participants will tend to stay in the system, otherwise
they may leave. We analyze user and miner strategies that are currently
possible in BitCoin-like implementations, and we show that existing
block-chain systems are not fair for their users. We finally discuss
new ways for improvement arguing that novel redistribution mechanisms
are needed to promote participation of all nodes.