Since the launch of Pi Network's Pi App, many Pi pioneers have known that there is a safety circle in the Pi App. By adding 5 other Pi Pioneers that you trust in your security circle, you can increase your computing power to obtain more Pi. But what is the use of this safety circle? Is it just a decoration, or does it really play a role in the operation of Pi Network? To understand the role of this security circle, let's first understand the consensus algorithm used by Pi Network.
Pi Network is based on the early cryptocurrency Stellar project. The github address of the open source Stellar project code is: The github address of the Stellar Lumens project code open source. Stellar has been running since 2014. You can think of Pi Network as an upgraded version of the Stellar Lumens project. Stellar uses the Stellar Consensus Protocol (SCP). SCP is an instance of Federated Byzantine Agreement (FBA), that is to say, SCP is built on FBA. SCP is also used to reach consensus.
Since Pi Network does not yet have open source code, we will first use the Stellar project that uses the Stellar Consensus Algorithm Protocol SCP to explain the confirmation process of a transaction with SCP.
In SCP, a quorum slice is a collection of a node and other nodes it believes it can trust. A quorum shard can convince specific nodes in the quorum shard to agree with other nodes in the quorum shard. For example, a node A in the quorum shard thinks that a transaction is an illegal transaction, and other nodes in the quorum shard that node A trusts think the transaction is a legal transaction. Then, other nodes in the quorum shard will The node can convince Node A through this trust relationship, so that Node A also believes that the transaction is a legitimate transaction.
Nodes in different quorum shards can form a quorum, and a quorum shard is a subset of a quorum. Quorum refers to the set of nodes that can satisfy a consensus agreement. For the confirmation of a transaction, that is, to determine whether a transaction is legal, it is first confirmed by the legal body sharding and then sent to the nodes in the legal body for voting. As long as more than 2/3 of the legal body nodes agree that the transaction is legal, the transaction can be truly confirmed, submitted and broadcast to the entire network, and finally written into the Stellar ledger, that is, the transaction is written into in the block. Otherwise, the transaction will be considered illegal and will not be submitted and broadcast.
The selection of nodes in the legal body is based on the trust, reliability and contribution of the nodes. In the Stellar Lumens project, nodes are mainly played by companies and institutions (such as IBM). This will have relatively large restrictions, which is not conducive to improving decentralization. Therefore, in order to allow ordinary users to participate more broadly and further improve decentralization, Pi Network allows personal devices to contribute and receive rewards at the protocol level, including mobile phones, laptops, and computers. Pi users can set up a security circle through the Pi App and set up other Pi users they trust. Through the trust relationship of the security circle, an extensive distributed trust relationship graph is formed. If these Pi users run Pi nodes again, then by setting up a security circle, it is equivalent to increasing the credibility of these Pi nodes, thereby better building legal body shards and legal bodies, and improving the security of blockchain operations. sex. In the traditional Byzantine consensus algorithm, the nodes in the quorum are pre-determined by the creator of the system at the beginning. Subsequent changes in the nodes in the quorum also need to be reviewed before they can take effect. The degree of centralization is high. Compared with the traditional Byzantine consensus algorithm, the selection of quorum nodes in the federated Byzantine consensus algorithm is mainly determined through trust relationships and is not subject to any central authority, so it is more decentralized.