Dash introduces LLMQ-based ChainLocks to mitigate 51% mining attacks
By Rafał - 2018-12-01
What are 51% mining attack?51% mining attack refers to an attack on blockchain which becomes possible when a single entity or a group of miners control more than 50% of the network’s mining hashrate, or computing power. The attackers can then interfere with the process of recording blocks and prevent new transactions from gaining confirmation, thus allowing them to pause payments between users. They can also reverse the transactions that were completed while they were in control of the network, thus making it possible for them to double-spend coins. Therefore, it is sometimes also referred to as double spend attack.
LLMQ-based ChainLocksDash explains the idea and working mechanism of ChainLocks in its recent blog post. The ChainLocks not only makes mining-based attacks theoretically impossible but also protects the network against selfish mining and chain reorganizations.As stated by Dash in its blog post “The idea of ChainLocks is to perform a verifiable network-wide measurement/vote of the “first-seen” rule. For each block, an LLMQ of a few hundred masternodes is selected and each participating member signs the first block that it sees extending the active chain at the current height. If enough members (e.g. >= 60%) see the same block as the first block, they will be able to create a P2P message (CLSIG) and propagate it to all nodes in the network. There are some more details to this process, especially when multiple miners find a block at approximately the same time.”
Effects and features offered by ChainLocks
- One of the most important feature offered by ChainLocks for normal users and merchants is that transactions can be considered fully confirmed after the first on-chain confirmation inside a block protected by it. Thus, it eliminates the need to wait for 6 or more confirmation to consider received transaction as secure.
- Transactions can no longer vanish from the chain as reorganization of locked block is not possible.
- Protects against selfish mining.
- Any secret chain (even if thousands of blocks longer) would be immediately invalidated if another honest miner publishes a valid block that receives a CLSIG before the secret chain is revealed.
- No consensus rules are affected. The longest-chain rule being one of the most important part of proof of work-based consensus will also be in effect but can be overridden by a valid CLSIG message.