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01 Thanos hard fork
ETC upgraded the node at a block height of 11,700,000, which is 03:48 on November 29, 2020. The upgraded node completed the code implementation in the ECIP-1099 proposal: lengthening the epoch.
Ethereum Classic (ETC) was originally the same as Ethereum (ETH), and every 30,000 blocks is an epoch. After each epoch is updated, the volume of the DAG file will be increased. After the upgrade, the epoch length of Ethereum Classic is doubled, and every 60,000 blocks is an epoch.
The DAG file in the ETH and ETC network is a data packet based on the Ethash algorithm. In ETH and ETC mining, the DAG file needs to be located in the video memory of the mining device to assist in mining. Its volume will increase with the increase of epoch. Before Thanos hard fork, ETC's DAG file volume has reached 4GB, which means that before Thanos hard fork, 4GB video memory cards cannot mine ETC.
After the upgrade is completed, the epoch length of ETC is doubled, and the volume of DAG files is greatly reduced, from the original 4GB to 2.47GB. At the same time, by changing the calculation method of epoch, ETC's mining algorithm has also been upgraded on the basis of the Ethash algorithm, becoming the Etchash algorithm, and initially leaving the ETH algorithm family.
This is the Thanos hard fork of ETC.
02 Reasons for Thanos hard fork
Reason 1: End ETH computing power control and get rid of the computing power attack dilemma
As the forked currency of ETH, ETC has been shrouded in the shadow of ETH while being sheltered by the big tree of ETH.
To a certain extent, before the hard fork of Thanos, ETC and ETH were a pair of clone brothers. The two used the same mining algorithm and almost the same code. All technological innovations on the ETH network can basically be The ETC network is realized, and ETC enjoys the huge technological dividend of ETH.
In addition, because ETC mining and ETH mining use the same mining algorithm, it is very easy to switch between each other. Millions of mining machines participating in ETH mining around the world only need a small part to flow into the ETC mining ranks. Form a strong scale effect.
However, due to the high dependence on ETH mining, the mining ecology and network security of ETC are extremely fragile: 1% of ETH computing power can attack the ETC network with computing power, or even 51% attacks. And 1% of ETH computing power can be purchased from Nicehash through a per-second billing method, which is extremely low cost; it can also be obtained by paying and renting from large miners, because there are not a few large ETH miners with more than 1% computing power. that's the truth:
In January 2019, the ETC network suffered multiple 51% computing power attacks, and mainstream exchanges such as Coinbase, Binance, Gate.io suffered heavy losses;
On August 1, 2020, the ETC network suffered a 51% computing power attack. The attacker double spent more than 800,000 ETC by reorganizing the ETC block, which directly caused the victim's economic loss of 5.6 million US dollars. At the same time, he participated in ETC mining The miners of the mine also suffered economic losses of tens of thousands of dollars. It is reported that the cost of the attacker's purchase of Ethash computing power to attack the ETC network in Nicehash is 17.5 BTC, which is approximately $200,000;
On August 5, 2020, the ETC network suffered another 51% computing power attack, and more than 4000 ETC blocks were reorganized;
On August 29, 2020, the ETC network suffered another 51% computing power attack. This time, as many as 7,000 ETC blocks were reorganized and related transactions were affected.
Several consecutive attacks have caused the "dark moment" of ETC and exposed major security risks of the ETC network. Exchanges have begun to extend the time for ETC entry (from half an hour to more than 2 weeks), and even many The exchange directly delisted ETC.
Miners have also suffered a lot of losses in many attacks. The extremely long time to account has dampened the enthusiasm of other miners to a certain extent. Therefore, there is a situation: even if the mining income of ETC far exceeds that of ETH, there is still no Enough miners participate in ETC mining. This in turn leads to more fragile ETC network security.
Figure 1 Changes in the computing power of the entire network after the ETC network was attacked in August
Therefore, ETC must change the algorithm and cut with ETH mining to prevent attackers from attacking the ETC network by obtaining ETH computing power at low cost.
Reason 2: Attract the computing power abandoned by ETH and strengthen the ETC ecosystem
The mining algorithms used by ETH and ETC increase the memory requirements of mining machines through the ever-increasing volume of DAG files, thereby enhancing their ASIC resistance.
ETH's DAG file will reach 4GB in December 2020, and all graphics cards with 4GB or less of video memory will be eliminated by ETH mining. This means that AMD 470/480/570/580 4GB video memory graphics cards, one of the main ETH mining forces, will withdraw from the ETH mining market in December.
This part of graphics cards was once popular with miners because of their high quality and low price and super high cost performance, and they accounted for a very high proportion of ETH mining equipment. When the ETH DAG file reaches 4GB, the computing power of a large number of 4GB graphics cards will be cleared, and the ETH network is bound to be greatly shaken. However, the ETH team has been trying to get rid of the influence of mining and promote the PoS consensus. Therefore, without harming network security, a significant reduction in the computing power of the entire network is very consistent with the official demands of ETH. They will not have any measures to save the 4GB video memory card. .
Miners with 4GB video memory graphics cards were once in a panic. Some miners who bought second-hand 4GB video memory graphics card mining machines may have just been stunned by the ultra-low price of the mining machines, and then they were dominated by the fear of no mining. . If there is a currency that can support mining with 4GB video memory and graphics card miners, a large number of miners will flock to it.
Figure 2 A large number of 3GB and 4GB video memory graphics card mining machines will flood into the ETC mining market
ETC chose to perform this Thanos upgrade at this time, just to solve the urgent need of 4GB video memory graphics card miners. By receiving the computing power eliminated by ETH, on the one hand, it gathers miners and expands the influence of the community; on the other hand, these have to be transferred to ETC. The network's graphics card will increase the computing power of the entire ETC network to an unprecedented level, and its network security will also be greatly improved.