A protocol capable of properly ensuring consensus among processes that fail to the fullest is considered t-resistant. A particular case of the problem of the simple value of consensus, called binary consensus, limits the entry and thus the exit domain to a single binary number. Although not very useful in themselves, binary consensus protocols are often useful as building blocks of broader consensus protocols, particularly for asynchronous consensus. On the other hand, an unauthorised consensus protocol allows everyone on the network to join dynamically and participate without prior authorization, but instead imposes another form of artificial costs or barriers to access in order to reduce the threat of the Sybil attack. Bitcoin introduced the first unleased consensus protocol, based on evidence of cryptographic work, in which participants compete to solve cryptographic puzzles and earn the right to commit blocks and earn rewards over their invested computing effort. Motivated in part by the high energy cost of this approach, successive unauthorised consensual protocols have proposed or adopted alternative participation rules for the protection of Sybil attacks, such as. B proof of use, proof of place and proof of authority. The formal requirements of a consensual protocol may include: A new implementation of the simultaneous object is called wait-free implementation, which can guarantee consensus in a finite number of steps. Is a certain type of object strong enough to solve consensus problems? Maurice Herlihy gave an “impossibility and hierarchy of universality”.  Many real-time peer-to-peer strategy games use a modified lockstep protocol as a consensual protocol to manage the state of play between players in a game. Each game action leads to a delta game state transferred to all other players in the game with a whole game state hashah.
Each player verifies the change by applying the delta to his own state of play and comparing the hashs of the game`s state. If the hashs do not agree, one vote will be voted and players with a minority state of play will be separated and removed from the game (known as Desync). Google has set up a distributed blocking library called Chubby.  Chubby manages blocking information in small files stored in a replicated database to achieve high availability in the event of an error. The database is implemented on an error-tolerant protocol layer, based on Paxos` consensus algorithm. In this diagram, Chubby`s customers communicate with Master Paxos to access/update the replicated protocol. That is, read/write in the files.  However, some simultaneous objects are universal, which means they can resolve the consensus between any number of processes and simulate all other objects.