Sequel to my previous post on bitcoin 51% attack and its effect, this is an updated (new) post of the previous one after taking correction and done more research about it.
Blockchain transactions that have already been mined are modified by the 51% attack.
The only way this is feasible is if one's mining power is greater than other miners'. The ability to mine the next block is determined by one's mining power in comparison to other miners. Due to the significant costs associated with controlling more than 50% of the network's total computing capacity, a 51% attack has never been attempted in the history of bitcoin and is unlikely to ever happen.
Here's an illustration of how it functions:
![](https://ip.bitcointalk.org/?u=https%3A%2F%2Fi.ibb.co%2FjJnsxwT%2FDBC0-CA75-7-B27-4630-A6-E0-E726-D4-DAD250.jpg&t=665&c=8v-QTMdUyN6Srw)
The above image shows (5 miners) whose total computational power is 500,000 hashes per second (h/s). Different hashes per second were generated by each of the 5 miners as seen in the image above. The first miner was able to produce 175,000 h/s, followed by the second miner that generated 100,000 h/s, the third generated 75,000 h/s, the fourth generated 125,000 h/s, and the fifth generated 25,000 h/s. They’re all struggling to find a hidden number that is unknown to them all and the person that gets the correct number will be able to unravel the puzzle (mine the next block). The likelihood of mining the next block is 35% for the first miner, 20% for the second, 15% for the third, 25% for the fourth, and 5% for the fifth.
The miner with the highest percentage of the total hashing power has the likelihood of finding the number first. Meanwhile, this is just a probability as the person with the lowest hashing power can also be lucky to unravel the puzzle first before others.
The bitcoin network's nodes have produced 190 million tera hashes per second as of February 2022. A tera hash is equal to 1,000,000,000,000. With 51% computational power, a miner or node (a group) may produce 96.9 million tera hashes per second, increasing his chances of creating the longest chain.
Chain reorganization occurs when nodes receive details of a valid chain with more proof of work than the chain they are currently following. A miner who has more than 50% of the hashrate will not have the ability to alter the upcoming block because it is not known yet, but can modify previous block in the blockchain by replacing them in favor of malicious chain with more work.
The bad person (who owns 51% hashrate power) has more control over the block reward and the ability to add the block to the blockchain with more than 51% hashrate power. The miners following the correct rule-see this and decline to accept the block. And as a result, the bad guy's work is pointless. You must manage several nodes and operate them simultaneously if you want to swiftly confirm your block and upload it to the blockchain.
Currently, a miner owning 51% hashrate and using it for an attack swiftly in seconds is impossible because at least 20% of the hashrate is owned by public companies. Attempting this will only cause the attacker problems and will face many lawsuits for such action.
![](https://ip.bitcointalk.org/?u=https%3A%2F%2Fi.ibb.co%2Fb6zr03Z%2FC288642-E-C623-4-E98-B223-216-C4-C08-BA7-C.jpg&t=665&c=NqpQ-GZ2lhb7dA)
Source:
https://learnmeabitcoin.com/technical/51-attackThe graphic above shows how much mining capacity every of the miner has. Only one miner (GHash.io), with a total mining power of 38.24% in June 2014, was close to crossing 50% threshold. This poses a serious risk of security for people who are learning about bitcoin interestingly for the first time. The distribution of power has improved, and that company is no longer running.
You can check how hash rate distribution has been shared over the years in this clip:
https://twitter.com/in3rsha/status/1159468260661895169If a 51% attack takes place, what will the consequences be for the bitcoin network?
Effects and consequencesIn the circumstances mentioned above, this person might take advantage of that to carry out the following transactions while in control:
* Use your bitcoins for reverse transactions and double spending.
* Changing confirmations for any transaction in the block chain that has already been confirmed before by other miners.
* Not accepting transactions that should be authenticated normally.
* Preventing fellow miners not to mine valid blocks.
The great inventor of bitcoin once said:
“As long as a majority of CPU power is controlled by nodes that are not cooperating to attack the network, they’ll generate the longest chain and outpace attackers”. – Satoshi Nakamoto
51% might be possible theoretically but as far as the bitcoin network is concerned, 51% is not practically feasible.
Source:
https://bitcoin.org/bitcoin.pdfSource:
https://medium.facilelogin.com/51-attack-a72d26786b23Source:
https://academy.bit2me.com/en/51-bitcoin-attack/Source:
https://en.bitcoin.it/wiki/Weaknesses#Attacker_has_a_lot_of_computing_powerSource:
https://learnmeabitcoin.com/technical/51-attack