Nodes are the fourth role in the Pi ecosystem and run on laptops and desktops instead of mobile phones. Similar to other blockchains, Pi Nodes will be responsible for validating transactions on a distributed ledger and resolving the challenges in maintaining a distributed currency by having all nodes come to a “consensus” on the order of new transactions that are being recorded.

Unlike nodes that use proof of work such as Bitcoin or Ethereum, Pi Node uses a different consensus algorithm based on the Stellar Consensus Protocol (SCP). In SCP, nodes form trusted groups (quorum slices) and only agree to transactions that those trusted nodes agree to. The security circles (See Pi FAQ: What are security circles?) from Pi mobile miners aggregate into a global trust graph that enables Pi Nodes to form quorum slices to determine who can and cannot validate transactions on the shared ledger.

Unlike most other crypto projects, the Pi Node will continue to follow the philosophy of user-centric design. Instead of requiring deep technical knowledge to set up a node, everyday people will be able to do that by installing a desktop application on their computers. Through this computer application, Pioneers can switch the node software on/off to make their devices available/unavailable for serving as a node.

Pi will continue to adhere to the methodology of progressive decentralization as it develops its Testnet. During the initial Testnet, Pi’s blockchain component of the node software will have a centralized layer in order to achieve faster iterations of scenario stress testing and adaptations of the consensus algorithm to accommodate the needs of Pi Network and its global community (See Section – Testnet Roadmap). This initial version of the node is the first step toward building the Pi Testnet and eventually the fully decentralized mainnet.

This version of the node includes two interfaces: the node interface and the desktop Pi App interface. Depending on the levels of participation defined in the section below, Pioneers can use the two interfaces accordingly. Every mobile user can download the node software to their computer and use its desktop Pi App interface because it’s a similar interface to the mobile app and will allow people to check their Pi balance, watch media content and use the Pi chats on their personal computer. Every Pioneer can also apply to be a Node through the node interface and install the blockchain component there. There will initially be a Selection Stage (See Section – Testnet Roadmap) for the Core Team to calibrate node selection criteria based on the device reliability and connectivity. When a node is selected by the Core Team, they’ll need to pass KYC to proceed to serve as a node on Testnet. See more details in the section below: Selection Process for Nodes and SuperNodes.

Levels of Node Participation
There are currently three levels of participation for Pioneers to use the Pi Node software on their computers.

Computer App
Computer App refers to only using the desktop Pi App interface of the node software. It enables Pioneers who want to interact with the Pi app from their computers, so it has similar functionalities to the mobile app. For example, many Pioneers have previously expressed that they want to be able to chat on Pi through their computers rather than phones. Hence, we designed the desktop Pi App interface on Pi Node software and combined this interface with the node software. Also, in the future, as more functionalities are added to the Pi App, e.g. Apps Platform and the various apps on the platform, some of them might be easier to access through the desktop interface than the mobile application.

Node
Node means that Pioneers access the node interface, finish installing necessary technical preparations based on instructions, and switch on/off the node interface to make their computer available to run the blockchain component after being selected to be a Node. Although they don’t participate in the consensus, they verify the validity of the blockchain and submit transactions to get recorded on the blockchain. In the future when Pi’s blockchains expand to more than securing a ledger, Nodes will expand to include computers opting in to contribute to collective hardware resources of the network, such as computation, storage, and bandwidth.

SuperNode
SuperNodes are the backbone of Pi’s Blockchain. They are responsible for reaching a consensus based on the algorithm to write the right transaction on the Pi ledger, in addition to all the responsibilities that a node performs. They’re also responsible for making sure other SuperNodes and Nodes get the latest state of the blockchain. SuperNodes also utilize the node interface and are initially selected by the Core Team. They need to be connected to the network 24/7 and have a reliable internet connection.

See the table below for a summary of the three levels of participation in Pi Node software, and the hardware and software requirements for computers at each level of participation.