Polkadot is an innovative multi-chain blockchain platform designed to achieve interoperability and shared security between different blockchains. This article will delve into the security mechanisms of Polkadot, with a particular focus on how its core and on-chain systems provide shared security for rollups, and how the parallel chain protocol ensures the availability and validity of the entire network.
The security architecture of Polkadot relies on its unique core and validator system. The parallel chains of Polkadot are connected to the core and relay chain, with each core guarded by a group of 5 validators that rotate between cores every minute and change members every 4 hours.
The primary chain (L1) sends block candidates with proofs to the core. When 3/5 validators in the core receive and verify the data, the L1 block candidate is backed up to the Polkadot relay chain. Subsequently, the core is occupied, and the backup distributes some erasure codes (used for reconstructing information for further dispute checks) and block candidate receipts (CR, recorded in the relay chain) to validators outside the core. Polkadot’s BABE (Block Authoring algorithm) selects a block author and includes the block candidate receipts in subsequent relay chain blocks, returning the core to an available state for receiving subsequent candidate information for backup.
In Polkadot 1.0, the L1 block is included in the relay chain every 12 seconds, and the core validator execution time is 0.5 seconds. In Polkadot 1.0, an L1 chain can occupy a core for a maximum of 2 years.
The parallel chain protocol allows efficient sharding of the network while maintaining strong security guarantees. The Availability and Validity (AnV) protocol describes the parallel chain protocol from the perspective of availability and validity. The main roles in the protocol include validators, who are responsible for validating the proof of validity of parallel chain blocks, and collators, who create proofs of validity for validation.
The parallel chain protocol’s main stages include the inclusion pipeline, where collators send parallel chain blocks along with proofs to validators for approval, and the approval process, where validators conduct additional checks and approve parallel chain blocks.
The AnV protocol emphasizes the availability and validity of parablocks before they are included in the final relay chain, dividing the process into five stages: three stages in the inclusion pipeline and two stages in the approval process.
Polkadot provides a robust security mechanism through its core and validator system, as well as the parallel chain protocol, ensuring efficient network operation and valid block validation. With ongoing technological development and protocol optimization, Polkadot is expected to continue to play a significant role in blockchain interoperability and shared security.
