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This article mainly introduces the relevant knowledge of what the Plasma framework is, the content is detailed and easy to understand, the operation is simple and fast, and has a certain reference value, I believe you will gain something after reading this Plasma framework article, let's take a look at it.

Plasma, as the two-tier expansion framework of ethernet, has been the focus of blockchain practitioners since it was proposed by Joseph Poon (founder of Lightning Network) and Vitalik Buterin (founder of Ethereum) in 2017 [1]. First of all, it needs to be clear that Plasma is essentially a framework, not a separate project, which provides off-chain solutions for a variety of different projects. This is an important reason why many people are confused about Plasma, because it is difficult to explain Plasma clearly in the absence of practical application scenarios. Therefore, understanding that Plasma is a framework is the key to understanding Plasma.

1 talking about the expansion of block chain

Before introducing Plasma, we have to introduce blockchain expansion. As we all know, Bitcoin and Ethereum, as the most widely used blockchain platforms, face the biggest problem of Scalability. It should be noted here that the scalability problem in the blockchain does not refer to a particular problem alone, but a series of challenges that the blockchain wants to achieve the vision of Web3.0 [3] and provide decentralized services to hundreds of millions of users. Although Etay Fong is known as the "world computer", this "computer" is single-threaded and can only handle about 15 transactions per second, which is dwarfed by the throughput of tens of thousands of mainstream Visa and MasterCard. Therefore, how to improve the scalability under the condition of ensuring the security of the blockchain is one of the urgent problems to be solved in the development of the blockchain.

At present, the solutions for blockchain expansion are nothing more than two directions: layer 1 (Layer 1) and layer 2 (Layer 2). One-layer capacity expansion is also known as on-chain (on-chain) capacity expansion. As the name implies, this kind of expansion solution requires changing the underlying protocol of the blockchain. But it also means that the blockchain needs to fork hard. This kind of expansion scheme is like converting the original single-core CPU into multi-core CPU, so that it can process computing tasks with multiple threads and improve the throughput of the whole network.

At present, the most typical layer expansion scheme is the "Sharding" proposed by Vitalik and his research team, that is, the blockchain is divided into different parts (shards), and each part handles the transaction independently. For more information about Sharding, please refer to the official Wiki of Etay Square [5].

Layer 2 expansion, also known as under-chain (off-chain) expansion, is also very understandable. This expansion scheme does not need to modify the underlying protocol of the block chain, but is completed by transferring a large and frequent amount of computing work to the "under-chain", and regularly or when needed, submit the calculation results under the chain to the "chain" to ensure its finality (finality). The core idea of the two-tier expansion is to take the underlying block chain as the consensus basis and use intelligent contracts or other means as a bridge between the chain and the chain. When fraud occurs, the users under the chain can still return to a certain state on the chain. Although moving computing down the chain will lose finality over a period of time, the cost is worth it, because doing so not only greatly improves the flexibility and scalability of the blockchain, but also greatly reduces the cost of trading for users. Transferring computing to the chain does not mean giving up security completely, because the ultimate security is guaranteed by the block chain that the underlying layer depends on, so the main concern of layer 2 expansion is how to ensure the security of the switching process up and down the chain. This idea was first used in the Lightning Network (Lightning Network) as one of the bitcoin expansion schemes, and achieved good results.

The Plasma introduced in this article is based on the two-tier expansion scheme of Ethernet Square, and similar solutions include State Channels and Trubit. Although these schemes face different problems, the basic idea is to transfer the complex computing to the chain. So, next we will enter the world of Plasma and take a peek!

2 understand Plasma

In the previous article, we have understood that Plasma is a two-tier expansion framework, so how to further understand what Plasma is? What distinguishes it from the other two-tier expansion schemes?

Plasma is also known as "blockchains in blockchains". Anyone can create different Plasma on top of the underlying blockchain to support different business needs, such as distributed exchanges, social networks, games, etc.

Here is an example to understand Plasma. Suppose Penguin creates a Plasma Chain called Game Chain. Users send some Ethernet coins to Game Chain in exchange for Token, which is used to buy in-game value-added goods such as skin. The operation of joining Game Chain is carried out on the chain, and the Taifang block chain locks this part of the assets and transfers them to Game Chain. After that, every time we buy virtual goods, the transaction will be transferred down the chain and accounted for by Penguin. This approach is almost the same as our experience of in-game purchase in real life, not only with quick settlement, but also with low handling fees (compared to the fees paid to miners on Etay Fong). So the question is, what if Penguin gets involved, changes its books and maliciously takes possession of our assets? At this time, we can submit the vouchers for each transaction to the etherfang block chain. if Penguin maliciously tampered with the account book, then we can not only successfully get back our assets, but also get some or all of the deposits previously deposited by Penguin's Game Chain.

Do you already understand how Plasma works roughly from the above example? But the above example is still too simple, involving only users and Penguin. Let's use the language of the block chain to parse the above example.

First of all, Penguin has created a series of intelligent contracts on the Ethernet Square main chain as a medium for Game Chain communication between the main chain and the sub-chain. These intelligent contracts not only specify some basic state transition rules in the subchain (such as how to punish the evil node), but also record the state in the subchain (the hash value of the blocks in the subchain). After that, Penguin can build its own sub-chain (which can be used to build a private chain in Taifang). The subchain is actually a completely independent block chain that can have dedicated miners and use consensus algorithms that are different from the main chain, such as PoS (Proof of Stake) and so on.

When the subchain is created, Penguin can use ERC721 contracts to create token as in-game merchandise (like Cryptokitty). However, it is important to note that all digital assets must be created on the ethernet main chain and transferred to the sub-chain through the smart contract of the Plasma sub-chain. Users also need to buy digital assets on the main chain and transfer them to the sub-chain. In the above example, Game Chain's smart contract locks assets on the main chain and then generates equivalent assets on the subchain. Then the user can completely break away from the main chain and trade on the sub-chain. Penguin plays the role of operator on the subchain. If everything works well, the miners in the subchain will pack the block normally, and when needed, operator will submit the hash value of the block to the main chain as the status update certificate of the subchain. In this process, the user does not need to interact with the main chain at all.

As we can see, moving complex computing operations down the chain does make the whole trading process easier. But without a strong consensus algorithm and a large number of participants, assets are very insecure on the subchain. Plasma gives us a risk aversion mechanism so that even if operator does evil, we can get back our own assets. The following figure (from [1]) briefly illustrates this process. In the figure, the transaction in Block 4 has been tampered with. Because Alice keeps all the chunk data in Plasma Chain locally, she can submit a transaction with an "anti-counterfeiting certificate (Fraud Proof)" to the main chain. If it proves to be valid, then the main chain rolls back the status from Block 4 to Block 3, and everything returns to normal. Participants in Plasmas Chain can also submit asset certificates at any time and return to the main chain.

We should have understood that the job of Plasma is not to protect the security of the subchain, but to ensure that users can safely retrieve their assets and return to the main chain when a security accident occurs. And use a series of economic incentives to reduce the occurrence of evil.

This is the end of the article on "what is the Plasma Framework?" Thank you for reading! I believe that everyone has a certain understanding of the knowledge of "what is the Plasma framework". If you want to learn more, you are welcome to follow the industry information channel.

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