Weak Subjectivity

Vitalik Buterin introduced the concept of weak subjectivity to explain a specific requirement in Proof of Stake (PoS) blockchain networks. In PoS networks, nodes depend on each other to determine the current state of the system, unlike the independent verification seen in Proof of Work (PoW) systems like Bitcoin, where nodes can verify the longest chain on their own.

Objectivity vs. Subjectivity:

● Objectivity: New nodes can independently identify the valid chain (e.g., Bitcoin).

● Subjectivity: Nodes rely on other nodes to determine the active chain.

Weak Subjectivity:

● Occurs when new nodes join the network or when nodes reconnect after a long period offline.

● Nodes must obtain the current state from other nodes to synchronize correctly.

Implications:

● Ensures network security and integrity in PoS systems.

● Addresses challenges in maintaining consensus without continuous online presence.

Weak subjectivity is vital for the efficient functioning of PoS blockchains, ensuring nodes can accurately identify the valid state of the network.