Majority attack - Revision history

MeshCollider: Reverted edits by Mala44 (talk) to last revision by Fresheneesz

2018-07-26T07:18:19Z

Reverted edits by Mala44 (talk) to last revision by Fresheneesz

← Older revision		Revision as of 07:18, 26 July 2018
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	A '''~~[https://medium.com/coinmonks/what-is-a-51-attack-or-double-spend-attack-aa108db63474~~ majority attack]''' (usually labeled '''~~[https://medium.com/coinmonks/what-is-a-51-attack-or-double-spend-attack-aa108db63474~~ 51% attack]''' or '''>50% attack''') is an attack on the network. This attack has a chance to work even if the merchant waits for some confirmations, but requires extremely high relative hashrate.		A '''majority attack''' (usually labeled '''51% attack''' or '''>50% attack''') is an attack on the network. This attack has a chance to work even if the merchant waits for some confirmations, but requires extremely high relative hashrate.

	The attacker submits to the merchant/network a transaction which pays the merchant, while privately mining a blockchain fork in which a [[double-spending\|double-spending transaction]] is included instead. After waiting for ''n'' confirmations, the merchant sends the product. If the attacker happened to find more than ''n'' blocks at this point, he releases his fork and regains his coins; otherwise, he can try to continue extending his fork with the hope of being able to catch up with the network. If he never manages to do this, the attack fails, the payment to the merchant will go through, and the work done mining will also go to waste, as any new bitcoins would be overwritten by the longest chain.		The attacker submits to the merchant/network a transaction which pays the merchant, while privately mining a blockchain fork in which a [[double-spending\|double-spending transaction]] is included instead. After waiting for ''n'' confirmations, the merchant sends the product. If the attacker happened to find more than ''n'' blocks at this point, he releases his fork and regains his coins; otherwise, he can try to continue extending his fork with the hope of being able to catch up with the network. If he never manages to do this, the attack fails, the payment to the merchant will go through, and the work done mining will also go to waste, as any new bitcoins would be overwritten by the longest chain.
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	==See Also==		==See Also==

	* [https://medium.com/coinmonks/what-is-a-51-attack-or-double-spend-attack-aa108db63474 What is a 51% attack]
	* [https://people.xiph.org/~greg/attack_success.html Attack success probability calculator]		* [https://people.xiph.org/~greg/attack_success.html Attack success probability calculator]
	* [[Irreversible_Transactions]]		* [[Irreversible_Transactions]]

Mala44 at 12:29, 25 July 2018

2018-07-25T12:29:14Z

← Older revision		Revision as of 12:29, 25 July 2018
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	A '''majority attack''' (usually labeled '''51% attack''' or '''>50% attack''') is an attack on the network. This attack has a chance to work even if the merchant waits for some confirmations, but requires extremely high relative hashrate.		A '''[https://medium.com/coinmonks/what-is-a-51-attack-or-double-spend-attack-aa108db63474 majority attack]''' (usually labeled '''[https://medium.com/coinmonks/what-is-a-51-attack-or-double-spend-attack-aa108db63474 51% attack]''' or '''>50% attack''') is an attack on the network. This attack has a chance to work even if the merchant waits for some confirmations, but requires extremely high relative hashrate.

	The attacker submits to the merchant/network a transaction which pays the merchant, while privately mining a blockchain fork in which a [[double-spending\|double-spending transaction]] is included instead. After waiting for ''n'' confirmations, the merchant sends the product. If the attacker happened to find more than ''n'' blocks at this point, he releases his fork and regains his coins; otherwise, he can try to continue extending his fork with the hope of being able to catch up with the network. If he never manages to do this, the attack fails, the payment to the merchant will go through, and the work done mining will also go to waste, as any new bitcoins would be overwritten by the longest chain.		The attacker submits to the merchant/network a transaction which pays the merchant, while privately mining a blockchain fork in which a [[double-spending\|double-spending transaction]] is included instead. After waiting for ''n'' confirmations, the merchant sends the product. If the attacker happened to find more than ''n'' blocks at this point, he releases his fork and regains his coins; otherwise, he can try to continue extending his fork with the hope of being able to catch up with the network. If he never manages to do this, the attack fails, the payment to the merchant will go through, and the work done mining will also go to waste, as any new bitcoins would be overwritten by the longest chain.

Mala44 at 15:37, 24 July 2018

2018-07-24T15:37:39Z

← Older revision		Revision as of 15:37, 24 July 2018
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	==See Also==		==See Also==

			* [https://medium.com/coinmonks/what-is-a-51-attack-or-double-spend-attack-aa108db63474 What is a 51% attack]
	* [https://people.xiph.org/~greg/attack_success.html Attack success probability calculator]		* [https://people.xiph.org/~greg/attack_success.html Attack success probability calculator]
	* [[Irreversible_Transactions]]		* [[Irreversible_Transactions]]
	* [https://medium.com/coinmonks/what-is-a-51-attack-or-double-spend-attack-aa108db63474 What is a 51% attack]
	[[Category:Technical]]		[[Category:Technical]]
	[[Category:Attack vectors]]		[[Category:Attack vectors]]

Mala44 at 15:31, 24 July 2018

2018-07-24T15:31:51Z

← Older revision		Revision as of 15:31, 24 July 2018
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	* [https://people.xiph.org/~greg/attack_success.html Attack success probability calculator]		* [https://people.xiph.org/~greg/attack_success.html Attack success probability calculator]
	* [[Irreversible_Transactions]]		* [[Irreversible_Transactions]]
	* [[https://medium.com/coinmonks/what-is-a-51-attack-or-double-spend-attack-aa108db63474 What is a 51% attack]]		* [https://medium.com/coinmonks/what-is-a-51-attack-or-double-spend-attack-aa108db63474 What is a 51% attack]
	[[Category:Technical]]		[[Category:Technical]]
	[[Category:Attack vectors]]		[[Category:Attack vectors]]

Mala44 at 15:31, 24 July 2018

2018-07-24T15:31:35Z

← Older revision		Revision as of 15:31, 24 July 2018
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	* [https://people.xiph.org/~greg/attack_success.html Attack success probability calculator]		* [https://people.xiph.org/~greg/attack_success.html Attack success probability calculator]
	* [[Irreversible_Transactions]]		* [[Irreversible_Transactions]]
			* [[https://medium.com/coinmonks/what-is-a-51-attack-or-double-spend-attack-aa108db63474 What is a 51% attack]]
	[[Category:Technical]]		[[Category:Technical]]
	[[Category:Attack vectors]]		[[Category:Attack vectors]]

Fresheneesz: clarification on when the mining effort will go to waste

2018-02-10T01:59:26Z

clarification on when the mining effort will go to waste

← Older revision		Revision as of 01:59, 10 February 2018
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	A '''majority attack''' (usually labeled '''51% attack''' or '''>50% attack''') is an attack on the network. This attack has a chance to work even if the merchant waits for some confirmations, but requires extremely high relative hashrate.		A '''majority attack''' (usually labeled '''51% attack''' or '''>50% attack''') is an attack on the network. This attack has a chance to work even if the merchant waits for some confirmations, but requires extremely high relative hashrate.

	The attacker submits to the merchant/network a transaction which pays the merchant, while privately mining a blockchain fork in which a [[double-spending\|double-spending transaction]] is included instead. After waiting for ''n'' confirmations, the merchant sends the product. If the attacker happened to find more than ''n'' blocks at this point, he releases his fork and regains his coins; otherwise, he can try to continue extending his fork with the hope of being able to catch up with the network. If he never manages to do this, the attack fails ~~and~~ the payment to the merchant will go through~~. The~~ work done mining will also go to waste, as any new bitcoins would be overwritten by the longest chain.		The attacker submits to the merchant/network a transaction which pays the merchant, while privately mining a blockchain fork in which a [[double-spending\|double-spending transaction]] is included instead. After waiting for ''n'' confirmations, the merchant sends the product. If the attacker happened to find more than ''n'' blocks at this point, he releases his fork and regains his coins; otherwise, he can try to continue extending his fork with the hope of being able to catch up with the network. If he never manages to do this, the attack fails, the payment to the merchant will go through, and the work done mining will also go to waste, as any new bitcoins would be overwritten by the longest chain.

	The probability of success is a function of the attacker's hashrate (as a proportion of the total network hashrate) and the number of confirmations the merchant waits for. For example, if the attacker controls 10% of the network hashrate but the merchant waits for 6 confirmations, the success probability is on the order of 0.1%. If the attacker controls more than half of the network hashrate, this has a probability of 100% to succeed. Since the attacker can generate blocks faster than the rest of the network, he can simply persevere with his private fork until it becomes longer than the branch built by the honest network, from whatever disadvantage.		The probability of success is a function of the attacker's hashrate (as a proportion of the total network hashrate) and the number of confirmations the merchant waits for. For example, if the attacker controls 10% of the network hashrate but the merchant waits for 6 confirmations, the success probability is on the order of 0.1%. If the attacker controls more than half of the network hashrate, this has a probability of 100% to succeed. Since the attacker can generate blocks faster than the rest of the network, he can simply persevere with his private fork until it becomes longer than the branch built by the honest network, from whatever disadvantage.

Taras at 09:13, 10 August 2017

2017-08-10T09:13:57Z

← Older revision		Revision as of 09:13, 10 August 2017
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	No amount of confirmations can prevent this attack; however, waiting for confirmations does increase the aggregate resource cost of performing the attack, which could make it unprofitable or delay it long enough for the circumstances to change or slower-acting synchronization methods to kick in. A majority attack was more feasible in the past when most transactions were worth significantly more than the block reward and when the network hashrate was much lower and prone to reorganization with the advent of new mining technologies.		No amount of confirmations can prevent this attack; however, waiting for confirmations does increase the aggregate resource cost of performing the attack, which could make it unprofitable or delay it long enough for the circumstances to change or slower-acting synchronization methods to kick in. A majority attack was more feasible in the past when most transactions were worth significantly more than the block reward and when the network hashrate was much lower and prone to reorganization with the advent of new mining technologies.

	A majority attack has never been executed on the Bitcoin network.		A majority attack has never been successfully executed on the Bitcoin network, but it has been demonstrated to work on some small altcoins.

	See also: [[Weaknesses#Attacker_has_a_lot_of_computing_power]]		See also: [[Weaknesses#Attacker_has_a_lot_of_computing_power]]

Belcher: /* See Also */ renamed 'double spending' -> 'irreversible transactions'

2017-07-09T19:19:47Z

See Also: renamed 'double spending' -> 'irreversible transactions'

← Older revision		Revision as of 19:19, 9 July 2017
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	* [https://people.xiph.org/~greg/attack_success.html Attack success probability calculator]		* [https://people.xiph.org/~greg/attack_success.html Attack success probability calculator]
	* [[~~Double spending~~]]		* [[Irreversible_Transactions]]

	[[Category:Technical]]		[[Category:Technical]]
	[[Category:Attack vectors]]		[[Category:Attack vectors]]

Belcher: added link to the weaknesses#attacker has a lot of computing power page

2017-07-04T14:36:09Z

added link to the weaknesses#attacker has a lot of computing power page

← Older revision		Revision as of 14:36, 4 July 2017
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	A majority attack has never been executed on the Bitcoin network.		A majority attack has never been executed on the Bitcoin network.

			See also: [[Weaknesses#Attacker_has_a_lot_of_computing_power]]

	==See Also==		==See Also==

Taras at 16:37, 8 July 2015

2015-07-08T16:37:14Z

← Older revision		Revision as of 16:37, 8 July 2015
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	[[Category:Technical]]		[[Category:Technical]]
			[[Category:Attack vectors]]