What is Polkadot? 5 minute to understand concept of Polkadot

By PengSeung | WhatIsCrypto | 23 Sep 2020

The author of this article is Bruno Škvorc, a developer and blockchain science worker from Croatia.


In 2015, Bruno joined the Ethereum ecosystem full-time and created popular science tutorials and programming courses for many novice developers, as well as tracking various news events. Starting in 2018, Bruno began to assist an ETH2.0 team in development; after 2019, Bruno became a professional technical science worker of the Web3 Foundation, committed to promoting the Web3 vision to ensure that anyone can access it anywhere Trusted Internet.




Author: Bruno Škvorc


Bruno is very concerned about decentralization, opposition to censorship, transparency and accountability, so he is passionate about immutable ledgers. He has a double master's degree in computer science and English language and literature. When conditions permit, Bruno intends to get involved in virtual reality.


The following article is a high-level summary of Polkadot after Bruno has assisted the Web3 Foundation for nearly 3 years, and after writing a large number of Polkadot science articles. The writing style of this article continues Bruno’s style, that is, as much as possible. In the professional case, it is guaranteed that everyone can understand it.


What is Polkadot? How is it different from existing blockchains? Where is the significance of Polkadot? Which public chains are in competition with Polkadot? This article will explain these issues in a very high level, so that those who are only familiar with the most basic blockchain terminology but do not have any professional technical knowledge can also fully understand them.


Polkadot's operating mechanism


Polkadot has a main chain based on Substrate called Relay Chain, and other blockchains linked to this main chain are called parachains.


There can be many types of parachains linked to the relay chain. They can be Bitcoin/Ethereum/Tezos/Edgeware. They can generate blocks in any self-consistent way. For example, Bitcoin can generate blocks with its own specifications, and Ethereum can use its own Tezos can generate blocks with its own specifications, and the smart contract blockchain Edgeware can also generate blocks with its own rules.




Relay chain, parallel chain, transfer bridge


Parachain gains immutability from the relay chain (Finality)-this is a terminal block (transaction on) that ensures that the transaction that has occurred will not be "back to its original shape".


Author's Note: Once the blockchain is forked, the original transaction on the block may be restored (for example, A transfers 10 BTC to B, and this BTC has been packaged and confirmed. Once the blockchain is forked, These 10 BTCs may return to A's account again, so it is very important to prevent transactions from being restored on the blockchain. On the Polkadot network, the relay chain gives the parachain the ability), the fork is There is a divergence between different software versions of the same blockchain, where a group of programs (or nodes) build blocks in one direction, and another group of programs build blocks in another direction.


On blockchains, bifurcations are very common. In general, the bifurcation chain will always fend for itself, but in extreme cases, the length of the bifurcation may exceed the original chain until it replaces the original chain and becomes the main chain. Transactions that occur on the chain will replace the transactions on the original chain.


The emergence of Polkadot is not to compete with any mainstream public chains in the existing blockchain world, including ETH2.0. On the contrary, Polkadot hopes to "hold up" all chains in order to achieve cross-chain communication between different blockchains-the goal is to establish a unified ecosystem for the decentralized blockchain world.


Cross-chain composability


We know that Bitcoin is an independent blockchain, and Ethereum is an independent blockchain. The two are different and operate independently-the two blockchains are like two closed walled gardens, they will be their own " "Exquisite" is enclosed in two small spaces-the value of locked Bitcoin cannot enter Ethereum, because you cannot transfer your Bitcoin to others in the absence of centralized trust.


Author's Note: Some people may ask, why do I have to transfer BTC to Ethereum? This is because the DeFi supporting Ethereum is a very prosperous ecosystem. Anyone can issue assets, obtain loans, or synthesize BTC into other assets to make their own assets circulate. In the Bitcoin network, you can’t do anything. , Can only watch his assets stand still.


"Polkadot is a cross-chain communication system."


On Polkadot, different blockchains can communicate with each other in a decentralized manner, allowing developers to develop cross-chain applications, allowing one parachain to send messages to another parachain. You can completely let go of your imagination. The message can be financial assets, chat information, atmospheric monitoring data, etc., of course, it can also be 10 bitcoins sent by investors from Bitcoin to Etherum.


Shared security


The relay chain is essentially a blockchain. Validators protect the security of this blockchain. The validator will run Polkadot nodes. The validator will occasionally be given the power to generate new blocks. They will be rewarded for their due diligence.




Validator, collector, nominator and angler on Polkadot


This article only involves validators on the relay chain


Anyone can become a validator, as long as they have enough chips behind them, the so-called chips here are the "national currency" DOT of the Polkadot relay chain. According to the number of DOT pledges, the first hundreds of validators will be elected in turn to become active Validator (active validators).


Author's note: If validators do a mess, they will be punished. For example, when the network needs them to work, their nodes are offline. At this time, their pledged DOT will be taken back, which is actually confiscated. Up.


The elected active validators will be randomly assigned to each parachain, and every few hours, such assignments will again be rotated in a random and unpredictable manner.


Every 6 seconds, the parachain will send a candidate block to the relay chain. This candidate block will be verified by validators who are online at these moments on the relay chain. If the verification is passed, the candidate block will be included in the block of the relay chain, and then the next candidate block will be generated in parallel. After the submission is completed, these blocks are immutable, and this is how the parachain grows carefree under the protection of the relay chain.


All parachains ultimately require validators on the relay chain to obtain the final authorization. The more parachains, the more validators are needed, and the higher the security of the entire network. Important reminder, if you want to become a validator, you must pledge DOT tokens. When you perform the role of validator, your DOT will be pledged in the Polkadot network.


In this way, the relay chain and the parachain share security, and each chain becomes a part of the anti-attack of the entire network.


Forkless upgrade and governance


Generally speaking, when the blockchain is upgraded, the fork is always inevitable: some nodes are upgraded, some nodes are not upgraded, and the nodes that have not been upgraded will always stay on the forked chain until these unupgraded chains are updated. The network is considered to be upgraded. What is more painful is that these nodes are distributed all over the world, and you cannot communicate with these anonymous nodes in real time.




Polkadot solves this problem by means of “on-chain runtime and on-chain governance”. On-chain runtime means that the code containing the rules for generating new blocks is stored on the chain. Therefore, nodes and programs running the blockchain only need to read this information, and they can be updated. So how do we update this code?


On-chain governance allows any DOT holder to initiate a referendum or vote on the referendum. A referendum is a proposal for changes to blockchain logic or data. Through governance, the community can make recommendations and vote on changes to the logic on the chain. Once the logic changes are voted on, they will be updated automatically, without the need to update the software or manual intervention.

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