In the Polkadot network, validators play a crucial role in ensuring the security and validity of the network by validating and attesting to the validity of a parachain’s block. This includes verifying the state transition, external transactions, the execution of any waiting posts in the ingress queue, and the final state of the egress queue.
The validation process
The validation process is simple, where a validator first finds a parachain block candidate from a collator or co-validator. This block candidate includes the block’s header, previous block’s header, external input data, egress queue data, and internal data to prove state-transition validity. The validator then locally validates the block by verifying the parent header’s identity, calling the specific parachain class’s validation function and returning a Boolean value that proclaims the validity of the block.
On the other hand, Parachain Collators are unbonded operators who perform many of the tasks of miners in present-day blockchain networks. They are specific to a particular parachain and are responsible for maintaining both the relay-chain and the fully synchronised parachain. The precise meaning of “fully synchronised” depends on the class of the parachain and includes the present state, any queued posts, and the historical transaction record. They are also responsible for creating a block candidate that includes the block’s header, external input data, egress queue data, and internal data to prove state-transition validity. Collators are incentivized to ensure that their block candidates are selected by validators since they earn transaction fees based on their blocks becoming canonical.
The parachains and their interaction
In the Polkadot protocol, the question of how to prevent one parachain from forcing another to do computation is left to the higher level.
A solution proposed is the use of a “break-in” contract within a parachain that allows a validator to be guaranteed payment in exchange for providing a certain amount of processing resources. However, this alone is not enough as the off-chain caller may not have the necessary value mechanism recognized by the contract.
To solve this, a secondary “breakout” contract in the source chain can be used to form a bridge between the two contracts, allowing for negotiation of value transfer between chains in order to pay for the computation resources on the destination chain.
Additionally, the protocol acknowledges that while the addition of a parachain is relatively cheap, it is not free. The addition of more chains can lead to a higher degree of latency and the potential for validators to be overwhelmed by over-burdensome validation algorithms.
Therefore, the community of stakeholders will need to be incentivized to add new chains, either through financial means or through the desire to add featureful chains to the relay. New chains added will also have a short notice period for removal, allowing for experimentation without risk of compromise.
Technologies
Here are the main technologies behind the Polkadot Project for those of you who would like to research deeper into the technology stack:
Conclusion
In conclusion, Polkadot is creating a scalable, heterogeneous multi-chain protocol that has the potential to be backwards compatible with pre-existing blockchain networks. The protocol relies on participants working in their own self-interest to create a system that can be extended in a free manner without causing additional costs for existing users.
We have provided a rough outline of the architecture and discussed the strengths and limitations of the design, as well as identifying potential next steps to ease those limitations and further improve the scalability of the blockchain solution. We also acknowledge that there are still open questions about the protocol that need to be addressed.