The future of Polkadot is a huge heterogeneous sharding architecture. in this huge structure. The relay chain is the central chain of Polkadot. All validators of Polkadot’s DOT are staked on the relay chain and verified for the relay chain. There are relatively few transaction types on the relay chain: governance mechanism interactions, parachain auctions, NPoS. The relay chain does not support smart contracts. The main responsibility is to coordinate the entire system and parachains. Other specific work is delegated to parachains with different functions.
Polkadot can support multiple execution slots. These sockets are like the cores on a computer processor (for example, a modern laptop processor might have eight cores). Each of these cores can run one process at a time. Polkadot allows these slots to use two subscription models: parachains and parathreads. Parathreads and parachains have the same API; their difference is economic. Parachains must retain DOTs for the duration of their slot leases; parathreads will pay per block. Parathreads can become parachains and vice versa.
Much of the computation that occurs across the Polkadot network will be delegated to specific parachain or parathread implementations that handle various applications. Polkadot places no restrictions on what parachains can do, except that they must be able to generate proofs validated by the validators assigned to the parachain. Proofs mainly verify the state changes of parachains, including specific applications, smart contracts, privacy or others.
Parachains connected to the Polkadot relay chain all share the security of the relay chain. Polkadot has shared state between the relay chain and all connected parachains. If the relay chain must be restored for any reason, then all parachains will also be restored. This is to ensure that the effectiveness of the entire system can persist and that no individual part is destructible.
Shared security, sometimes referred to in the documentation as pooled security, is one of the unique value propositions of parachains joining the Polkadot network. At a high level, shared security means that all parachains connected to the Polkadot relay chain by renting parachain slots will benefit from the economic security provided by the relay chain validators.
The concept of shared security differs from interchain protocols built on bridge architecture. For bridge protocols, each chain is considered sovereign and must maintain its own set of validators and economic security.
Polkadot overcomes the security scalability problem because it attracts all economic incentives to the relay chain and allows parachains to take advantage of stronger security at genesis. Sovereign chains have to put more effort into increasing the value of their tokens to make them sufficiently secure against well-funded attackers.
On Polkadot, this difference between chain security will not exist. When a parachain is connected to Polkadot, the relay chain validator is integrated as a safener for the state transition of that parachain. Parachains will only need to run a few collector nodes to keep validators up to date with state transitions and the overhead of proving witnesses. Validators will then check if they are assigned to a parachain. In this way, new parachains will immediately benefit from Polkadot’s overall security, even if they have just been launched.
Parachains are maintained by network maintainers called collators. The role of the collector node is to maintain a full node of the parachain, retain all the necessary information of the parachain, and generate new candidate blocks to pass to the relay chain validator for verification and inclusion in the shared state of Polkadot. The incentive to collect human nodes is an implementation detail of parachains. Unless parachains implement regulations, they do not need to stake or own native tokens on the relay chain.
Before Polkadot can confirm that a state transition has occurred on the parachain, the proof of the new state transition occurring on the parachain must be verified against the registered state transition function (STF) stored on the relay chain. A key constraint on parachain logic is that it must be verifiable by relay chain validators. The most common form of verification is a bundled proof of state transition, called a Proof of Verification (PoV) block, which is submitted from one or more parachain collectors to a validator for inspection.
The “parachain consensus” is special in that it will follow the Polkadot relay chain. Parachains cannot use other consensus algorithms that provide their own finality. Only the sovereign chain (which must be bridged to the relay chain via a parachain) can control its own consensus. Parachains can control how and who creates blocks. Polkadot guarantees efficient state transitions. Enforcing block finality outside the context of the relay chain goes beyond the trust Polkadot provides.
In Polkadot 2.0, it is expected to include nested relay chains, which means that parachains can connect multiple relay chains. Nominators secure the relay chain by choosing good validators and staking DOT. Validators secure the relay chain by staking DOT, validating the collector’s proof, and reaching consensus with other validators. The selected quasi-validator is one of 297 validators randomly selected (per epoch) to participate in the verification, creating a validator pool of 200 quasi-validators.
These actors play a vital role in adding new blocks to the relay chain as well as all parachains. This allows parties to complete cross-chain transactions through the relay chain. Parachain validators participate in some form of off-chain consensus and submit candidate receipts to the tx pool for block producers to be included on-chain. Relay chain validators guarantee that each parachain follows its unique rules and can pass messages between shards in a trustless environment.
Posted by:CoinYuppie，Reprinted with attribution to:https://coinyuppie.com/the-operation-principle-of-polkadot-relay-chain/
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