Bitcoin Forum
March 25, 2017, 08:00:52 AM *
News: Latest stable version of Bitcoin Core: 0.14.0  [Torrent]. (New!)
 
   Home   Help Search Donate Login Register  
Pages: [1]
  Print  
Author Topic: Shouldn't 51% attack really be >50% attack?  (Read 923 times)
statix
Newbie
*
Offline Offline

Activity: 12


View Profile
July 02, 2012, 07:33:57 AM
 #1

Why is it commonly known as 51% attack when, as far as I know, you'll only need to have >50% of hashing power to successfully pull out the attack.

The term has bothered me quite a bit for awhile.
1490428852
Hero Member
*
Offline Offline

Posts: 1490428852

View Profile Personal Message (Offline)

Ignore
1490428852
Reply with quote  #2

1490428852
Report to moderator
Bitcoin addresses contain a checksum, so it is very unlikely that mistyping an address will cause you to lose money.
Advertised sites are not endorsed by the Bitcoin Forum. They may be unsafe, untrustworthy, or illegal in your jurisdiction. Advertise here.
1490428852
Hero Member
*
Offline Offline

Posts: 1490428852

View Profile Personal Message (Offline)

Ignore
1490428852
Reply with quote  #2

1490428852
Report to moderator
1490428852
Hero Member
*
Offline Offline

Posts: 1490428852

View Profile Personal Message (Offline)

Ignore
1490428852
Reply with quote  #2

1490428852
Report to moderator
1490428852
Hero Member
*
Offline Offline

Posts: 1490428852

View Profile Personal Message (Offline)

Ignore
1490428852
Reply with quote  #2

1490428852
Report to moderator
Gareth Nelson
Hero Member
*****
Offline Offline

Activity: 722


View Profile
July 02, 2012, 07:36:43 AM
 #2

Why is it commonly known as 51% attack when, as far as I know, you'll only need to have >50% of hashing power to successfully pull out the attack.

The term has bothered me quite a bit for awhile.

Because the 50.000001% attack isn't as catchy
the joint
Legendary
*
Offline Offline

Activity: 1792



View Profile
July 02, 2012, 07:38:37 AM
 #3

Why is it commonly known as 51% attack when, as far as I know, you'll only need to have >50% of hashing power to successfully pull out the attack.

The term has bothered me quite a bit for awhile.

Because the 50.000001% attack isn't as catchy

Yeah, it's kinda like how "we are the 47%" isn't as catchy as "we are the 99%"

But I admit, I have thought the same thing.

Meni Rosenfeld
Donator
Legendary
*
Offline Offline

Activity: 1932



View Profile WWW
July 02, 2012, 07:49:00 AM
 #4

I usually call it the >50% attack.

1EofoZNBhWQ3kxfKnvWkhtMns4AivZArhr   |   Who am I?   |   bitcoin-otc WoT
Bitcoil - Exchange bitcoins for ILS (thread)   |   Israel Bitcoin community homepage (thread)
Analysis of Bitcoin Pooled Mining Reward Systems (thread, summary)  |   PureMining - Infinite-term, deterministic mining bond
ribuck
Donator
Legendary
*
Offline Offline

Activity: 826


View Profile
July 02, 2012, 08:02:24 AM
 #5

There's not really a hard limit for the percentage.

If an attacker has 47%, they might get lucky and maintain the longest chain for 6 blocks, which is enough for a devastating attack. On the other hand, they might have 53% for a while, and not manage a 6-block attack during that time.

Satoshi did a mathematical analysis of this in section 11 of his paper.

So I think "51% attack" is a good name for this attack, even though it's not a complete explanation.
Meni Rosenfeld
Donator
Legendary
*
Offline Offline

Activity: 1932



View Profile WWW
July 02, 2012, 08:43:29 AM
 #6

There's not really a hard limit for the percentage.

If an attacker has 47%, they might get lucky and maintain the longest chain for 6 blocks, which is enough for a devastating attack. On the other hand, they might have 53% for a while, and not manage a 6-block attack during that time.

Satoshi did a mathematical analysis of this in section 11 of his paper.

So I think "51% attack" is a good name for this attack, even though it's not a complete explanation.
With 47% the attacker has a chance to succeed, but no certainty. With >50% he is guaranteed to win eventually, no matter how many blocks are waited (though "eventually" can be a very long time, on average inversely proportional to the excess).

1EofoZNBhWQ3kxfKnvWkhtMns4AivZArhr   |   Who am I?   |   bitcoin-otc WoT
Bitcoil - Exchange bitcoins for ILS (thread)   |   Israel Bitcoin community homepage (thread)
Analysis of Bitcoin Pooled Mining Reward Systems (thread, summary)  |   PureMining - Infinite-term, deterministic mining bond
mrb
Legendary
*
Offline Offline

Activity: 1176


View Profile WWW
July 02, 2012, 08:58:32 AM
 #7

The right term is majority attack.
Gareth Nelson
Hero Member
*****
Offline Offline

Activity: 722


View Profile
July 02, 2012, 09:11:14 AM
 #8

Why is it commonly known as 51% attack when, as far as I know, you'll only need to have >50% of hashing power to successfully pull out the attack.

The term has bothered me quite a bit for awhile.

Because the 50.000001% attack isn't as catchy

Yeah, it's kinda like how "we are the 47%" isn't as catchy as "we are the 99%"

But I admit, I have thought the same thing.

Nice quote!

53% of the US population pay taxes
DannyHamilton
Legendary
*
Offline Offline

Activity: 1736



View Profile
July 02, 2012, 03:44:43 PM
 #9


Nice quote!

53% of the US population pay taxes

Actually, I'm pretty sure 100% of the U.S. population pays taxes, but we will avoid getting into a political discussion in this thread.

The quality of posts has dropped to such a low level that all users who are participating in a paid signature campaign are added to my ignore list. If you'd like a copy of the list to improve your browsing experience, you can find it here: https://bitcointalk.org/index.php?topic=973843.0 (Updated 2016-1-4)
Pages: [1]
  Print  
 
Jump to:  

Sponsored by , a Bitcoin-accepting VPN.
Powered by MySQL Powered by PHP Powered by SMF 1.1.19 | SMF © 2006-2009, Simple Machines Valid XHTML 1.0! Valid CSS!