Towards An Enhanced Reputation System for IOTA's Coordicide

Reputation plays a fundamental role in the blockchain ecosystem, as it provides means to assign trust levels to participating nodes. Reputation is usually gained in time: The higher the fair participation of a node to the network, the higher its reputation. IOTA's Coordicide proposes a reputation system based on an asset named Mana. This reputation system is the base of the Coordicide's primary security protection. At present, IOTA assigns to nodes an amount of Mana equivalent of the amount of transferred funds only. However, this may lead to privacy leakage on nodes' status and may not be sufficient to fully characterize the behavior of a node in the network. Furthermore, the Mana reputation system is currently susceptible to monopoly, eclipse, and spamming attacks. An efficient and secure reputation system shall comprehend a larger number of factors to provide security and reliability.In this paper, we propose Enhanced Mana (eMana), a theoretical model for the IOTA reputation system accounting for nodes' good or bad behaviour based on their assigned tasks. We model each of the Coordicide modules having direct or indirect connections with the reputation system. In eMana the behavior of a peer node can be transparently analyzed by the other peers; thus, it is infeasible to modify the reputation value. Theoretically, eMana is flexible enough to include possible new modules' behaviour and provides a strict hard-To-gain reputation. To the best of our knowledge, eMana is the first mathematical model for Coordicide's enhanced reputation based on nodes' multi-dimensional behaviour. Additionally, eMana is generic and flexible, and may also be adaptable to other Distributed Ledger Technology (DLT) systems.