4 ms·

In block chain, 51% of the network can decide to modify the ledger to do things that aren't true. That's all it takes to completely change how much money is in

In block chain, 51% of the network can decide to modify the ledger to do things that aren't true. That's all it takes to completely change how much money is in my account in a "distributed" bank. I don't own it, and it's certainly not robust against demagogues. Demagogues are by definition political opportunists who play on populism to advance their politics. If democratic elections have a vulnerability to them, so certainly do "distributed systems" where a simple majority has enough power to control "history"

Y7ZCQtNo39 9y ago
So if a majority of participants (50% + 1 of the network) wanted to say, "rob" the wealthy top 1% of wallets and redistribute wealth by rewriting the history of the blockchain, nothing could stop them?
- bloominglotus 9y ago
  Technically the unit of measurement is hashing power, rather than % of nodes or participants, but there is an underlying 51% problem with blockchain. The attack surface is similarly limited; they couldn't really "rob" the wealthiest wallets, but they could prevent their transactions from ever happening. They could also spend cryptocurrency they don't really have. Here's an intro: https://en.bitcoin.it/wiki/Weaknesses#Attacker_has_a_lot_of_computing_power https://en.bitcoin.it/wiki/Weaknesses#Attacker_has_a_lot_of_...
- deleted 9y ago
  [deleted]
- Dagger2 9y ago
  You can't just transfer money however you like, even if you had complete control of the blockchain. Transactions still need to be signed by the private key of the wallet involved. You could put a transaction with an invalid signature into the blockchain, but then the chain would be rejected by clients because of the invalid transaction.
  - slededit 9y ago
    The clients could be rewritten to accept the "invalid" block. That would cause a fork between the modified and unmodified clients. Like fiat currency, the only thing maintaining the definition of a legal block is the software the majority of the network choose to run.
    - Dagger2 9y ago
      They could indeed, but which users and companies would switch to that forked chain knowing that it's worthless? Having a lot of hashing power doesn't let you control the software that other people are running.
Jabanga 9y ago
>In block chain, 51% of the network can decide to modify the ledger to do things that aren't true. 51% is not enough to modify the ledger. A hard fork requires an overwhelming majority to support it. Otherwise, the cost of fragmentation would be immense, and outweigh any benefit those effecting the hard fork could hope to gain from the hard fork.

Y7ZCQtNo39 9y ago

So if a majority of participants (50% + 1 of the network) wanted to say, "rob" the wealthy top 1% of wallets and redistribute wealth by rewriting the history of the blockchain, nothing could stop them?

bloominglotus 9y ago
Technically the unit of measurement is hashing power, rather than % of nodes or participants, but there is an underlying 51% problem with blockchain. The attack surface is similarly limited; they couldn't really "rob" the wealthiest wallets, but they could prevent their transactions from ever happening. They could also spend cryptocurrency they don't really have. Here's an intro: https://en.bitcoin.it/wiki/Weaknesses#Attacker_has_a_lot_of_computing_power https://en.bitcoin.it/wiki/Weaknesses#Attacker_has_a_lot_of_...
deleted 9y ago
[deleted]
Dagger2 9y ago
You can't just transfer money however you like, even if you had complete control of the blockchain. Transactions still need to be signed by the private key of the wallet involved. You could put a transaction with an invalid signature into the blockchain, but then the chain would be rejected by clients because of the invalid transaction.
- slededit 9y ago
  The clients could be rewritten to accept the "invalid" block. That would cause a fork between the modified and unmodified clients. Like fiat currency, the only thing maintaining the definition of a legal block is the software the majority of the network choose to run.
  - Dagger2 9y ago
    They could indeed, but which users and companies would switch to that forked chain knowing that it's worthless? Having a lot of hashing power doesn't let you control the software that other people are running.

Jabanga 9y ago

>In block chain, 51% of the network can decide to modify the ledger to do things that aren't true. 51% is not enough to modify the ledger. A hard fork requires an overwhelming majority to support it. Otherwise, the cost of fragmentation would be immense, and outweigh any benefit those effecting the hard fork could hope to gain from the hard fork.