Ethereum's Scaling Solution: The Past and Present of Plasma (3)

In the previous article, I introduced how Plasma gradually lost its former glory after its birth, as the cryptocurrency bear market came and people made more objective and rational judgments, because it created more problems while solving them.

In Plasma, every user must monitor and verify all transactions in the Plasma MVP chain in order to discover illegal activities and exit the MVP chain. However, the cost of monitoring and verifying these transactions is very high.

And once a user enters Plasma to trade, it is often difficult to exit. Because when a user attempts to exit, he must first submit an exit request and wait for a period of time after submitting the exit request. This waiting period is called the "challenge period". During the challenge period, any user can present evidence to prove that the user's exit request is illegal (for example, the user illegally mined or stole other people's digital assets, etc.) to reject the user's request. Therefore, even if the exit request is legal, it can only be executed after the challenge period ends, and this process may take up to 1 week.

The worse case is: if there is an operator who controls the transaction data but does not make it public, and a user needs to leave Plasma to retrieve funds, then each user in Plasma can only withdraw their own amount based on the state given by the last valid transaction in Plasma (Note: to prevent fraud by malicious operators, the order in which users leave Plasma is determined by the time of their last valid transaction).

In the worst case, if all users want to leave Plasma, all valid states must be submitted to Ethereum and accept the "challenge" during the challenge period. Since Plasma has no limit on the number of users, but the processing capacity of Ethereum blocks is very limited, if the entire valid state of Plasma is submitted to Ethereum for processing, it will completely block Ethereum, causing the transaction processing time to be greatly delayed or even indefinitely. This is called the "mass exit problem."

In the cryptocurrency bear market in 2018, Ethereum followers began to realize that Plasma MVP technology was not as perfect as they had imagined. The problems encountered by Plasma in practice were almost insurmountable, or even unsolvable. People believed that the direction pioneered by Plasma was a dead end. At the same time, Ethereum was still struggling with congestion, and Ethereum 2.0, which was expected to fundamentally solve the congestion problem of Ethereum, was nowhere in sight.

In mid-2018, although the price of Ethereum continued to fall, the Ethereum research community continued to improve Plasma and continuously iterated the design of Plasma. Finally, a new generation of Plasma technology emerged, which is "Plasma Cash".

Vitalik is also one of the main designers of Plasma Cash. In his opinion, Plasma Cash technology has greatly improved transaction performance and can also solve the headaches caused by Plasma. People are starting to be optimistic again, and even believe that this new technology can reach hundreds of thousands of TPS per second.

Before we dive into Plasma Cash, let’s review a few of the problems Plasma MVP encountered:

1) When an operator does something evil, there will be a “group departure problem”.

2) Users need to wait for a challenge period before officially leaving Plasma.

3) Users must monitor and verify all Plasma transactions.

So in what aspects does Plasma Cash innovate Plasma? How does it solve these problems? We will continue to share in the next article.