As a mechanism to counter 51% attacks, Ethereum Classic is implementing a new security solution identified as “Modified Exponential Subjective Score” (Modified Exponential Subjective Scoring o MESS).
As reported by the Ethereum Classic team, MESS is an adaptation of the “Exponential Subjective Scoring” security framework, proposed by Ethereum co-founder Vitalik Buterin in 2014. It’s designed to prevent malicious reorganizations in blockchain networks, and prevent attacks of 51%.
Regarding the choice of this solution, raised by the leader of the blockchain from which ETC forked in 2016, the Ethereum Classic brief highlights that there is progress compared to Buterin’s original approach.
“We have evolved this idea 6 years ago towards what we anticipate will be a robust, efficient and uncompromising solution,” they state. To do this, they developed the ECIP-1100 improvement proposal, presented to the community last September.
According to published information by Ethereum Classic this October 1, MESS was approved by developers and community members.
The post explains that the tool was activated on Mordor Testnet on September 28 and has passed stress tests and simulated attacks. The developers believe that MESS will help secure the network. “It will protect the miners’ rewards and exchanges of possible double expenses, allowing deposits / withdrawals and reducing confirmation times ”.
Activation on the Ethereum Classic mainnet is scheduled at the height of block 11,380,000, estimated for October 10, 2020. “It will be included as a default Core-Geth configuration for ETC Mainnet from version v1.11.15 and later,” the developers note. Therefore, they recommend to the miners of the network download and update to that version node software.
The note clarifies that some of the network-enabled clients, such as Hyperledger Besu and Multi-Geth, do not have the MESS security function activated.
“The Besu team is working to add the MESS security feature in the future,” they state, adding that Parity Ethereum, OpenEthereum, and Geth-Classic are outdated clients. “If you are currently running one of these clients, you will need to switch to Core-Geth to be protected by MESS and for continued development and support.”
51% attacks get more expensive
According to ETC Labs, MESS prevents 51% attacks by “red flagging” attempts to reorganize large blocs.
“Thanks to this alert, 51% attacks become more expensive to propagate across the network.” It happens because MESS qualifies as suspicious the large reorganizations used to launch these attacks. In doing so, they become significantly more difficult and prohibitively expensive. This is because they consume a high amount of sustained terahashes for many hours in order to be successful.
Additionally, with the new tool nodes must make a subjective decision to prefer the string segments they see first, about the segments they see later.
This preference is defined by setting what Vitalik calls a “severity” assigned to the segments present in a node’s view, relative to those that are not yet. The scale of this preference is parameterized by the ratios of relative difficulty (total) of the competing segments and the age of their common ancestor. In this way, the segment that appears for the first time is weighted with a “severity” that the competing segment must match to be accepted.
The developers add that MESS respects the idea that “the code is law”, as a principle of the network. It means that the heaviest chain wins. According to ETC Labs, the new protocol respects this rule.
If the preferred chain is the first one the node sees (most likely since propagating blocks in public is more profitable for honest miners), “building a long and potentially malicious chain in secret will not be feasible”. This is expected to end the 51% attack attempts.
In this way, the efficiency of the algorithm will be driven by the level and consistency of adoption by the nodes, “particularly by the honest mining majority.”
MESS arises as part of the search for solutions to face the security issues of the Ethereum Classic network, after having suffered three attacks of 51% during the month of August.
Regarding the causes of these attacks, they argue that they were derived from a “low hashrate that caused the consensus algorithms to yield inconvenient and undesirable finality rates.” This fact made it “relatively cheap to dominate the chain’s recent history.”
As responses to the 51% attacks, ETC Labs had implemented “defensive mining”. A cooperation plan was established with pools of mining to maintain a more constant hash rate and increase it when necessary, as published by CriptoNoticias last August.
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Ethereum Classic activates 51% anti-attack protocol devised by Vitalik Buterin