All Möbby users are by default able to send and receive tokens (without needing substantial reputation); however, only parties with non-zero reputation, who declare themselves as available on the blockchain will be able to participate in the PoR protocol. At an initial bootstrapping phase of the system the reputation of parties is decided by the genesis block, PoR participation is restricted to a set of core nodes (servers), that receive no block rewards—i.e., their rewards are distributed to the users endorsing them. In subsequent phases, the system will increase this node set with the final goal of full decentralization where anyone can become an active Möbby node.

Through the lifetime of the system, parties can choose to be nodes (servers) or simple users (endorses). Simple users contribute to the computation of the node’s reputation, by a novel endorsement mechanism but do not themselves run the consensus mechanism. In the fully decentralized era of Möbby, a user will be able to join or leave the set of active nodes (recall that participating in this set comes with various perks in terms of reputation and token-incentives) by posting a special message on the blockchain declaring themselves available. A bootstrapping mechanism will mandate the period after such a declaration that the new node can start accumulating rewards.

Taking a gradual approach to decentralization, as above, ensures the stability of the Möbby blockchain. A similar approach is taken with respect to which factors are accounted for in computing a party’s reputation. More concretely, in a first decentralization phase, parties’ reputation will depend only on the system itself. The Möbby blockchain will leverage novel AI techniques for computing reputation. In a nutshell, by endorsing each other, parties build a reputation graph that can be ported to a special-tailored PageRank-inspired mechanism to compute the reputation of each party. The novel part of this mechanism is that it will create incentives for parties who wish to maximize their rewards to truthfully report their belief on the credibility/reputation of other parties towards a stable and fair reputation-system that does not suffer from the manipulability of PageRank.

On the other hand, parties can lose reputation by being accused with evidence of misbehavior in the PoR or fallback PoS protocols—an example of evidence being signatures of two conflicting transaction sets in the PoR protocol. This significantly reduces the party’s reputation. A party can also lose reputation by endorsing a reputation party, who misbehaves in the PoR or PoS protocols (even if the endorser does not misbehave themselves). While the reputation penalty is less for the endorsers than the misbehaving party, this penalty incentivizes parties to only endorse parties who they trust to behave honestly and prevent attackers from taking advantage of the endorsement system. Lastly, a party’s effective reputation is decreased if they lose endorsements from other parties.

Computing reputations as above will give the Möbby blockchain a controlled and self-regulated envi- ronment to get properly bootstrapped and decentralized. However, the goal of Möbby is far beyond an inward-looking reputation system. It aims to use the reputation of different actors (even in tasks not directly relevant to the system itself) to both obtain a better prediction of their honesty, and most, importantly, via its incentives, provide a platform for more transparent and truthful recommender systems. As such, in a future version, the Möbby team plan to import to the blockchain data from existing recommender systems, and via partnerships allow global, unified access to this data and enable incentives that can sanitize them (e.g., by deterring malicious reviews).