CoinDesk Report:
Author: Filippo Franchini, Web3 Foundation, Translation: OneBlock+
Polkadot is an innovative multi-chain blockchain platform designed to achieve interoperability and shared security among different blockchains. This article explores in detail Polkadot’s security mechanisms, focusing particularly on how its core and on-chain systems provide shared security for rollups, and how parachain protocols ensure the overall network’s availability and efficiency.
Polkadot’s Security Architecture
Polkadot’s security mechanism relies on its unique core and validators system. Parachains on Polkadot are connected to the core via a relay chain, with each core guarded by a group of 5 validators called dots, rotating among cores every minute and changing members every 4 hours.
Layer 1 (L1) chains send block candidates with proofs to the core. Once 3 out of 5 validators in a core receive and verify the data, the L1 block candidate is backed up to the Polkadot relay chain.
(In the image: orange, R1)
Subsequently, the core is engaged (red in the image), and backer-uppers distribute some erasure codes (used for reconstructing information for further dispute checking) and block candidate receipts (CR, recorded on the relay chain) to validators outside the core.
Polkadot’s Block Authoring Babe (BABE) selects a block author, including block candidate receipts in subsequent relay chain blocks (blue in the image, R2), and the core becomes available again for receiving subsequent candidate information for backup.
In Polkadot 1.0 without asynchronous support, L1 blocks are included in the relay chain every 12 seconds, with core validator execution time of 0.5 seconds.
In Polkadot 1.0, an L1 chain can occupy a core for a maximum of 2 years.
Parachain Protocol Overview
Source: https://wiki.polkadot.network/docs/learn-parachains-protocol
The parachain protocol facilitates the process of creating and including a parachain’s blocks into the relay chain through a repeatable parallel process. This protocol enables efficient sharding of the network while maintaining robust security guarantees.
Availability and Validity (AnV) Protocol describes the parachain protocol from the perspectives of availability and validity. Validators are responsible for validating proofs of validity (PoV) of parachain blocks within specified timeframes. Validators stake bonds on-chain and may face partial or full confiscation for malicious behavior.
Collectors create PoV for validators to verify, requiring familiarity with specific parachain transaction formats and block creation rules, as well as complete state access permissions.
Key Stages of the Parachain Protocol
Inclusion Pipeline: Collectors send parachain blocks (parablocks) along with PoV to validators. Validators check if parablocks follow state transition rules and sign results. Upon sufficient positive results, blocks are backed up and included in the relay chain pending approval.
Approval Process: Validators conduct additional checks; if passed, parachain blocks are approved.
Data Availability and Validity Protocol (AnV)
AnV protocol provides an alternative perspective on the parachain protocol, emphasizing that parablocks must be both available and valid before inclusion into the final relay chain. It consists of five stages: three in the inclusion pipeline (parachain phase, relay chain submission phase, availability and unavailability phase) and two in the approval process (task assignment and secondary (validity) check, chain selection).
Polkadot, through its core and validators system, and parachain protocols, offers robust security mechanisms ensuring efficient network operations and valid block verification. With ongoing technological advancements and protocol optimizations, Polkadot is poised to continue playing a crucial role in blockchain interoperability and shared security.