The 51% threats on Blockchain

[Amphenomenon]

In Blockchain before a block is added to the blockchain its first validated by miners. This is done by voting, the group with the highest percentage in voting choose the block added to the blockchain. If someone has a 51% of a Blockchain, then they have the chance of choosing the block added to Blockchain because they have over 50% of the vote for the block to be added. This makes it possible for the 51% attack. One thing to note is that, this attack is not a vulnerability on the technical design of the blockchain but rather a consequence of its decentralized nature.

This has higher chances to occur on Blockchain using PoW mechanism, it has lower chances to work on PoS and others but Bitcoin is already safe from this, through the fact that the capital needed to get the ASICS machines and other equipment is beyond what the hackers can earn, since also using expensive machines like ASICs rather than GPU protect against such attack. This hack has affected Blockchain like bitcoin gold, litecoin and others simply because they have few Community/miners unlike Bitcoin.

   In a successful 51% attack double spending is possible, this allows attackers to spend same coin twice. There are other possible issues which can the blockchain can face after a successful 51% hack example is reverse transaction and Preventing new transactions from being confirmed and others.

The 51% is not as easy as it seems even with the required hashrates it is still possible because other factors has to be considered.

Also this do not entirely destroy the blockchain i.e it can be restored to its actual working flow but this do leave a red flag on the blockchain.

Since the 51% hack is not a vulnerability on the technicality of the blockchain but the mechanism on how the blockchain works whereby the amount of miners play an important role for the protection against such hack while altcoins using PoW mechanism suffers from such hack since they have few miners. So what is another alternative for these Blockchain to protect themselves ?

Can any altcoin which fall victim of such hack be trustworthy to you ?

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[Charles-Tim]

This is done by voting, the group with the highest percentage in voting choose the block added to the blockchain.

I do not know about altcoins, but there is nothing like group voting if it is bitcoin.

In a successful 51% attack double spending is possible, this allows attackers to spend same coin twice.

Yes, there is double spending, but not in a way that the attacker can spend the coin twice. This is how it happens, the coin that has been confirmed before would be reversed and be spent by the attacker. That is why it is good to let your bitcoin transaction to have more confirmations because the higher the confirmation, the lower the possibility of such double spending. 6 confirmations is advised.

[Odohu]

In a successful 51% attack double spending is possible, this allows attackers to spend same coin twice.

Yes, there is double spending, but not in a way that the attacker can spend the coin twice. This is how it happens, the coin that has been confirmed before would be reversed and be spent by the attacker. That is why it is good to let your bitcoin transaction to have more confirmations because the higher the confirmation, the lower the possibility of such double spending. 6 confirmations is advised.

Double spending is an old form of attack that did not last long before people became aware of it. It's solution is as simple as not releasing Bitcoin in a p2p transaction until payment is confirmed released. With proper awareness and basic security consciousness, I don't see that as much of a threat.

[Charles-Tim]

Double spending is an old form of attack that did not last long before people became aware of it. It's solution is as simple as not releasing Bitcoin in a p2p transaction until payment is confirmed released. With proper awareness and basic security consciousness, I don't see that as much of a threat.

There are different means of double-spending attack. 51% attack is a different one but can be one of them. In 51% attack, transactions that have been confirmed can be double-spent by the attacker and that is the reason it is advised for people to wait for more confirmations. But bitcoin blockchain has a very huge hashrates and it is distributed in a way there will not be 51% attack. So for this reason, if a transaction has one confirmation already, it is safe. Another thing that can occur is chain reorg, but if the confirmed transaction has been reversed, likely it would be confirmed again. But for a high amount of bitcoin, it is advised to wait for more confirmations.

Another double-spending is the use of replace-by-fee to invalidate a transaction, which I think is the double-spending that you are referring to. Another one is if nodes ae dropping a transaction from their mempool after 14 days in which the sender can double-spend the coin. Another one is if the the mempool is full, low fee unconfirmed transaction will be dropped for high fee unconfirmed transactions, the sender can be able to double-spend the coin. These are the ones you are referring to, not 51% attack.

[Coyster]

Op your post no dey easy to understand at all, if na Bitcoin network you been dey talk about, mind you say na nodes dey validate transactions, na the miners come they confirm am. There is also nothing such as a voting system, for Bitcoin network miners they compete amongst themselves to mine a block, them they compete using their computational power, and any miner wey win go mine that particular block.

This has higher chances to occur on Blockchain using PoW mechanism, it has lower chances to work on PoS

Pos dey centralized, and you fit talk say coins wey dey use POS algorithm dey centralized. POW make sense well well, and e dey decentralized, na why Bitcoin dey use this algorithm and would never change or move to another one.

Can any altcoin which fall victim of such hack be trustworthy to you ?

51% attack aside, quite a lot of altcoins no dey trustworthy and they were only created to make their owners rich, na why people dey call altcoins pump and dump scheme, and na true.

[Amphenomenon]

I do not know about altcoins, but there is nothing like group voting if it is bitcoin.

Oh, please can you explain how this work on Bitcoin

In a successful 51% attack double spending is possible, this allows attackers to spend same coin twice.

Yes, there is double spending, but not in a way that the attacker can spend the coin twice. This is how it happens, the coin that has been confirmed before would be reversed and be spent by the attacker. That is why it is good to let your bitcoin transaction to have more confirmations because the higher the confirmation, the lower the possibility of such double spending. 6 confirmations is advised.

this is what I was trying to say but it seems mine is too vague. This is done by the attackers creating an alternate of the blockchain without the transaction for others to validate whereby they reverse the transaction from the main Blockchain.

[Charles-Tim]

Oh, please can you explain how this work on Bitcoin

Miners make a candidate blockchain (which include unconfirmed transactions). The miners in the process of trying to mine the next block, they compete with each other to guess a valid nonce that is used to know the transactions and other data contained in a block. The nonce is used to know the exactly miner that mine a block. Nodes validate mined block and the transaction it contains and route it to other nodes.

this is what I was trying to say but it seems mine is too vague. This is done by the attackers creating an alternate of the blockchain without the transaction for others to validate whereby they reverse the transaction from the main Blockchain.

Exactly, this is what 51% attack is.

[Fivestar4everMVP]

Good thing is, Pow is now very much outdated, there are no more POw blockchains being released this days, what we have now is majorly DPos and POS itself - this two blockchain infrastructures or consensus mechanisms looks very same in their physical operations, but are a bit different in their code base, but again, the general good thing about this is that, they are built in such a manner that a 51% or other simpler attack are close to not possible, but not entirely Impossible.

51% attack is still possible in POS and DPos blockchain consensus mechanisms if and when a validator or some group of validators or 51% or more; of the entire token staked on the blockchain network, though this is close to impossibility since it's very expensive for a validator to own more than 50 percent of the entire token staked on the network.