Timeline for What can an attacker with 51% of hash power do?
Current License: CC BY-SA 3.0
14 events
| when toggle format | what | by | license | comment | |
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| Jan 6, 2022 at 8:21 | comment | added | oblio | > Since this attack doesn't permit all that much power over the network, it is expected that no one will attempt it. * * * He he. The first "powers" listed would allow centralization of the protocol, so a state level agent can and will most likely try it if they find it interesting from a political point of view. They'd basically turn Bitcoin into a regular state controlled currency. | |
| Dec 19, 2021 at 15:40 | comment | added | MCCCS | would continue harming legacy software until they go bankrupt. However since SegWit is more or less adopted everywhere today such an infeasible attack would have a small impact. It'd help to read about how SegWit works as a soft fork to understand what I described. | |
| Dec 19, 2021 at 15:39 | comment | added | MCCCS | @JohnD Soon after SegWit is activated but not much later miners can reverse the soft fork and spend the coins which are anyonecanspend outputs for legacy clients but safe segwit outputs for newer clients which would cause a chain split and if 51% wants to reverse SegWit, exchanges who haven't yet updated their clients would follow the chain with the highest accumulated PoW, in which miners could spend SegWit outputs to wherever they like. This is not possible if all clients and enterprises adopt SegWit at day 1 but since SegWit was designed as a soft fork an infeasible 51% attack by miners | |
| Dec 19, 2021 at 12:34 | comment | added | John D | how is that so? @MCCCS | |
| Feb 4, 2021 at 6:07 | comment | added | adrian | @JoeMB Two years late, but to answer your question for anyone who may stumble across this thread: miners try different nonces, hoping to find one which causes the numeric value of the block header's hash to be lower than a difficulty target. That difficulty target is dynamically adjusted based on network hashrate. You specify the target in the block header. Bitcoin nodes will reject blocks with artificially low difficulty to prevent cheating. | |
| Jun 13, 2018 at 3:19 | comment | added | Joe MB | @IlyaSaunkin, how would an attacker create a low-difficulty block? Wouldn't he still have to find the random nonce in every block in order to be approved by everyone once the fork is merged back? | |
| Jun 5, 2018 at 21:01 | comment | added | eran otzap | how would an attacker change an historic block ? | |
| Aug 29, 2017 at 15:47 | comment | added | MCCCS | A 51% attacker can steal coins from SegWit addresses. | |
| Nov 12, 2013 at 8:59 | comment | added | Stéphane Gimenez | Yes sure. Longer is meant in terms of proof-of-work. | |
| Nov 12, 2013 at 7:30 | comment | added | Ilya Saunkin | from the documentation: The client accepts the 'longest' chain of blocks as valid. The 'length' of the entire block chain refers to the chain with the most combined difficulty, not the one with the most blocks. This prevents someone from forking the chain and creating a large number of low-difficulty blocks, and having it accepted by the network as 'longest'. | |
| Sep 7, 2011 at 2:47 | vote | accept | ripper234 | ||
| Sep 6, 2011 at 19:17 | history | edited | Stéphane Gimenez | CC BY-SA 3.0 |
Better explanation/wording.
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| Sep 6, 2011 at 18:59 | history | edited | Stéphane Gimenez | CC BY-SA 3.0 |
added 4 characters in body
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| Sep 6, 2011 at 18:54 | history | answered | Stéphane Gimenez | CC BY-SA 3.0 |