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Bitcoin => Bitcoin Technical Support => Topic started by: bushstar on January 29, 2013, 01:05:14 PM



Title: Looking for a guide to 51% attacks
Post by: bushstar on January 29, 2013, 01:05:14 PM
So I'm wondering if there are any good guides to running a 51% attack on BitCoin?

Might seem a bit daft and implausible for Bitcoin but I could use this guide to inform myself of the possible threats to Bitcoin and I can re-purpose it to test alt-coins. There are some alt-coins with very low hashrate, I'd be interested to see if I could take over an alt-coin for a small while.


Title: Re: Looking for a guide to 51% attacks
Post by: novusordo on January 29, 2013, 06:42:47 PM
1. Control >50% of the network hashrate.
2. Mine blocks faster than the rest of the network.
3. ? ? ?
4. PROFIT!

Try it!


Title: Re: Looking for a guide to 51% attacks
Post by: Ploo on January 29, 2013, 07:38:39 PM
So I'm wondering if there are any good guides to running a 51% attack on BitCoin?

Might seem a bit daft and implausible for Bitcoin but I could use this guide to inform myself of the possible threats to Bitcoin and I can re-purpose it to test alt-coins. There are some alt-coins with very low hashrate, I'd be interested to see if I could take over an alt-coin for a small while.

You would ignore any blocks mined by the rest of the network and mine on your own until your chain is longer than the rest of the network which given you control 51% of the network hashrate is statistically inevitable. You would then spend some coins somewhere, wait for however many confirmations your recipient requires and receive your irreversible goods. You can now broadcast your longer chain and in one of the blocks include a transaction that spends the coins elsewhere so the original recipient never gets to claim them.


Title: Re: Looking for a guide to 51% attacks
Post by: chrisLG on January 29, 2013, 07:41:49 PM
There you go: http://eprint.iacr.org/2012/248.pdf


Title: Re: Looking for a guide to 51% attacks
Post by: Meni Rosenfeld on January 29, 2013, 07:57:32 PM
There you go: http://eprint.iacr.org/2012/248.pdf
That paper is about the exact opposite of >50% attacks - trying to double-spend unconfirmed transactions.


Title: Re: Looking for a guide to 51% attacks
Post by: bushstar on January 30, 2013, 10:30:46 AM
So I'm wondering if there are any good guides to running a 51% attack on BitCoin?

Might seem a bit daft and implausible for Bitcoin but I could use this guide to inform myself of the possible threats to Bitcoin and I can re-purpose it to test alt-coins. There are some alt-coins with very low hashrate, I'd be interested to see if I could take over an alt-coin for a small while.

You would ignore any blocks mined by the rest of the network and mine on your own until your chain is longer than the rest of the network which given you control 51% of the network hashrate is statistically inevitable. You would then spend some coins somewhere, wait for however many confirmations your recipient requires and receive your irreversible goods. You can now broadcast your longer chain and in one of the blocks include a transaction that spends the coins elsewhere so the original recipient never gets to claim them.

Okay. I get this. Mine with 51% but do not broadcast the block chain. Spend old coins on the network and then broadcast my chain without those coins being spent.

I'll now go find a suitable atl-coin testnet to try this out. Thanks for the help.

If someone does find a comprehensive guide for doing such dastardly deeds please do post a reference to it here.


Title: Re: Looking for a guide to 51% attacks
Post by: BitcoinSuite on January 30, 2013, 05:16:54 PM
There you go: http://eprint.iacr.org/2012/248.pdf

We need more serious people like those folks - focused on legitimate research.
Thanks for digging it up!