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Author Topic: Solution to a 51% attack?  (Read 5067 times)
knight22
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October 12, 2013, 05:43:34 AM
 #1

Seems someone came up with a solution to a 51% attack with goldcoin.
http://gldcoin.com/documents/GoldCoin_0.7_51percent_defense_october_11_2013.pdf

I'm not an expert in cryptography at all but does it sounds legit and if so, is it applicable to bitcoin?

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gmaxwell
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October 12, 2013, 06:16:32 AM
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It doesn't sound legitimate at all. It sounds like the writing of someone who doesn't even have a basic understanding of the problem space.

It ignores the existence of sybils, assuming that an attacker is confined to appear to be a single peer to the whole network. This is crazy, If not for sybils there would be no need for mining at all you could just have nodes produce blocks round-robbin or just directly sense a majority of nodes for consensus.

Even the false assumption that sybils don't exist isn't enough for this scheme, as it requires (see the last page) a centrally announced "checkpoint" to make the protection reliable as nodes enter and leave the network.  Moreover, it doesn't describe how it's mechanism wouldn't falsely partition the network in the event that some kind of topology disruption resulted in the network having a small min-cut (e.g. fiber cuts between continents), this wasn't adequate explained but many proposals along these lines in the past have resulted in schemes which would never re-converge again after a modest partitioning: from one currency two result, and all coins can be spent twice (one in each side).

Bitcoin will not be compromised
meta.p02
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October 12, 2013, 06:37:35 AM
 #3

What stops me from doing this:

1. Control a large number of nodes.
2. On all except one, broadcast a chain that is always 1 block behind the main chain.
3. Suddenly from the last one release 4 blocks in quick succession. Now you win by 3 blocks (and don't trigger the 51% defense).


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October 12, 2013, 06:47:41 AM
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It doesn't sound legitimate at all. It sounds like the writing of someone who doesn't even have a basic understanding of the problem space.

It ignores the existence of sybils, assuming that an attacker is confined to appear to be a single peer to the whole network. This is crazy, If not for sybils there would be no need for mining at all you could just have nodes produce blocks round-robbin or just directly sense a majority of nodes for consensus.

Even the false assumption that sybils don't exist isn't enough for this scheme, as it requires (see the last page) a centrally announced "checkpoint" to make the protection reliable as nodes enter and leave the network.  Moreover, it doesn't describe how it's mechanism wouldn't falsely partition the network in the event that some kind of topology disruption resulted in the network having a small min-cut (e.g. fiber cuts between continents), this wasn't adequate explained but many proposals along these lines in the past have resulted in schemes which would never re-converge again after a modest partitioning: from one currency two result, and all coins can be spent twice (one in each side).
It's funny because not only would this proposed system not even work, the goons who proposed it don't even have the technical skills to put it into place to begin with.

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October 12, 2013, 08:41:42 AM
 #5

The solution to a 51% attack is never let one entity amass that amount.

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October 12, 2013, 08:50:50 AM
 #6

Who ever wrote this, seriously needs a basic tutoring in exactly what a 51% attack is....The whole thing is so flawed I don't even know where to begin.

A 51% attack in no way has to involve a Double Spend on an exchange. I can kill your block chain with a 51% attack and never spend a single coin. It seems to me the author doesn't understand what a 51% attack is or the difference between a 51% and a Double Spend attack. They are entirely two different exploits and neither one will be limited by a 5 blocks in 10 minutes limitation....

Also let's not forget about either one of the Time Warp Exploits, the ArtForz version from 2011 or the new and improved BCX version that no one yet has seemed to mitigate at all.

I like Goldcoin and I like Microguy but if you guys keep posting basic stupid crap like this, someone will come along and shred your coin for you just for the hell of it and no it won't be me. I can think of about 5 or 6 right off the bat that would do it just for the challenge.


~BCX~




Where can I read more on this?  I understand that double spend attempts don't even necessarily require 51% of total network.  It's just that with 51% you are statistically guaranteed success.  Right?  But how does a 51% attack kill the blockchain?
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October 12, 2013, 09:08:22 AM
 #7

There is none, high network hashrate would reduce the chances

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October 12, 2013, 11:57:03 AM
 #8

Nice to see some constructive criticism. All this will be usefull to improve new update.
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October 12, 2013, 01:17:54 PM
 #9

Quote
In a nut shell, a 51% attacker controls the majority of the network's mining power, and since the network automatically chooses the longest blockchain to be the correct one, this gives the attacker control over transactions. This allows them to repeatedly spend the SAME coins on an exchange over and over again.

This paragraph and the rest of white paper is full of nonsense unfortunately. First of all, not everyone who has 51%+ of network hash power is an attacker. One may mine blocks like anyone else and include other users' transactions in the blocks mined. On the other hand, one may mine empty blocks only and ignore other users' transactions completely, thus paralysing any coin movement on the network. It may be done with less than 51% of hash power to a lesser success though. Double spending is a different matter which involves two block chain forks with coins spent on one of them and unspent on the other which must become the primary chain eventually. Time warps are for difficulty manipulations at retargets. Finally, your defence concept is based on a false assumption of the attacker coming from a single IP or whatever you use for identification. There may be dozens if not hundreds of peers deployed worldwide for a distributed attack. There is no reliable decentralised solution currently to fight back 51% attacks of any kind.

"If you've got a problem and have to spread some coins to make it go away, you've got no problem. You've got an expence." ~ Phoenixcoin (PXC) and Orbitcoin (ORB) and Halcyon (HAL)
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October 12, 2013, 02:24:31 PM
 #10

Who ever wrote this, seriously needs a basic tutoring in exactly what a 51% attack is....The whole thing is so flawed I don't even know where to begin.

A 51% attack in no way has to involve a Double Spend on an exchange. I can kill your block chain with a 51% attack and never spend a single coin. It seems to me the author doesn't understand what a 51% attack is or the difference between a 51% and a Double Spend attack. They are entirely two different exploits and neither one will be limited by a 5 blocks in 10 minutes limitation....

Also let's not forget about either one of the Time Warp Exploits, the ArtForz version from 2011 or the new and improved BCX version that no one yet has seemed to mitigate at all.

I like Goldcoin and I like Microguy but if you guys keep posting basic stupid crap like this, someone will come along and shred your coin for you just for the hell of it and no it won't be me. I can think of about 5 or 6 right off the bat that would do it just for the challenge.


~BCX~





This garbage was posted officially as GoldCoin Propaganda...
So it must have been vetted by several people...
I for one, am tired of these clowns running their pie holes with idiotic predictions, etc.

Get a grip, its just a basic, deflationary LTC clone (with g-o-l-d in the name)...
Its reached the point where crippling GLD would help clean up the Alt Space.


akumaburn
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October 12, 2013, 03:15:04 PM
 #11

Most of the above points are MOOT.
@ gmaxwell there is no CENTRAL checkpoint, all bans and checkpoints are done locally and in memory only
@ meta.p02 there are a few attacks that bypass this system, but this system was designed primarily to stop most attacks from being profitable.
@Hazard , Please don't talk about technical skill when you don't possess any.
@BitcoinEXpress Anyone with a significant amount of resources can break virtually anything that relies on p2p communication... this is meant to act as a stopgap measure, and as the number of nodes grow, so does the feasibility of this defense. Remember even when submitting with multiple nodes there will be a convergence point to a legitimate peer, and then that legitimate peer will be banned for transmitting too quickly, thereby segmenting the network for 4 hours but keeping many legitimate users safe.
@User705 Correct, it's possible to sloatboat your way around the system over time, but such an attack would be noticable and thus far easier to prepare for(on the dev side of things).
@ghostlander it's not based on the assumption of a single peer, remember that in p2p networks as the network grows larger there is always a convergence point, it will segment the network for 4 hours before allowing them to continue, the segmentation is limited by how many nodes the attacker controls and is a good defense for a large network.
@QuantPlus We don't post propaganda, perhaps you should look to one of the other altcoins? We've backed up every claim we've made to date.

Stop arguing over semantics, this was designed to stop some double spending attacks, basic difficulty attacks, and multipools(and it does that very well). When I say "virtual immunity" - I don't mean total immunity, I mean immunity from pretty much anyone out there who realizes that the cost of the attack would be greater than the gain.

The system is designed to cut off an affected portion of the network in the event of a multi-pronged attack, they will simply reconnect in 4 hours and continue on the main chain. This may make it unfeasible for something with < 100 nodes, but for bitcoin its perfectly usable.
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October 12, 2013, 03:27:25 PM
 #12

Goldcoin, such a great coin!



You're a pathetic scam artist. Nothing more.

Hazard.. maker of almost ALL shitcoins.

http://thecryptoblog.com/the-anatomy-of-a-scamcoin-7-things-to-know-before-investing-in-an-altcoin-wait/

Check our cryptsy BTC trade history, most of those initial coins were traded away months ago.

Not to mention the line is ONLY FLAT BECAUSE OF A DIFFICULTY ATTACK OF 2GH/S.

Here's the real graph:


Any coin that first starts out needs liquidity, and for some reason idiots like you neglect difficulty.

Those coins that had a "fair start" weren't even fair at all because by the time most people started mining the difficulty was much higher than it was for those at the beginning. This is one of the things GoldCoin was designed to work around with those initial super blocks.
AZIZ1977
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October 12, 2013, 03:34:08 PM
 #13

The Goldcoin community is at least trying to do something for the crypto community to find somekind a solution to the 51% attacks. We have started something and from here on we build/improve it. To be honest I personally like all this critisme/advise, because it can all be used to improve this defense.
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October 12, 2013, 03:34:17 PM
 #14

Any coin that first starts out needs liquidity, and for some reason idiots like you neglect difficulty.

Those coins that had a "fair start" weren't even fair at all because by the time most people started mining the difficulty was much higher than it was for those at the beginning. This is one of the things GoldCoin was designed to work around with those initial super blocks.
Hilarious. You heard it hear folks: GLDCoin dev thinks giving a handful of people a good portion of all coins in existence is a great idea.

That's not about liquidity. That's about lining your pockets. A coin doesn't even need liquidity when it launches, because there's no economy for it other than speculative trading.

The focus of a coin's launch should be getting the coin into as many different hands as possible. Something that GLD failed miserably at, by design.

akumaburn
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October 12, 2013, 03:42:20 PM
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Any coin that first starts out needs liquidity, and for some reason idiots like you neglect difficulty.

Those coins that had a "fair start" weren't even fair at all because by the time most people started mining the difficulty was much higher than it was for those at the beginning. This is one of the things GoldCoin was designed to work around with those initial super blocks.
Hilarious. You heard it hear folks: GLDCoin dev thinks giving a handful of people a good portion of all coins in existence is a great idea.

That's not about liquidity. That's about lining your pockets. A coin doesn't even need liquidity when it launches, because there's no economy for it other than speculative trading.

The focus of a coin's launch should be getting the coin into as many different hands as possible. Something that GLD failed miserably at, by design.

We excelled at spreading GLD.. so keep your delusions to yourself please, almost all of those coins were traded in the first week on cryptsy, https://www.cryptsy.com/markets/view/30 (view first week history).

Two, it is about liquidity as most people do not like holding 0.1 coins in their wallet, there is a psychological factor against dealing with decimals for people.
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October 12, 2013, 03:49:36 PM
 #16

We excelled at spreading GLD.. so keep your delusions to yourself please, almost all of those coins were traded in the first week on cryptsy, https://www.cryptsy.com/markets/view/30 (view first week history).
Yeah. You gave a shitload of GLD away for basically free, which was promptly dumped for profit onto bagholders.

Great launch guys. Truly.

Two, it is about liquidity as most people do not like holding 0.1 coins in their wallet, there is a psychological factor against dealing with decimals for people.
Awful reasoning, and unless someone is mining with an old Pentium 3, they will have more coins than that.

Keep trying to justify your shitty launch. You guys are delusional.

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October 12, 2013, 04:26:44 PM
 #17

Akumaburn and AZIZ,

Why are you even bothering with this thread?

Did you ever notice how most of the old timers and serious developers do not have anything to do with him?

He is entertainment, plain and simple. He writes in a blog about developers he has never had any real conversation with and just assumes his observations are correct. He has a small band of newbies that cheer him on.

His 15 minutes will fade and another will take his place.

As the cypto community continues to grow, more like him will come on scene and he will be only a small voice among many others who proclaim to be "internet celebrities". The community will also grow in those that are of reasonable mind, and will work to make a difference and grow the community. Put your efforts into appealing to the later, and realize the former are nothing more then a daily chuckle.  Cheesy
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October 12, 2013, 04:39:47 PM
 #18

Akumaburn and AZIZ,

Why are you even bothering with this thread?

Did you ever notice how most of the old timers and serious developers do not have anything to do with him?
Oh, the irony.

Did you ever notice how most of the old timers and serious developers do not have anything to do with goldcoin? Cheesy

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October 12, 2013, 05:58:14 PM
 #19

The Goldcoin community is at least trying to do something for the crypto community to find somekind a solution to the 51% attacks. We have started something and from here on we build/improve it. To be honest I personally like all this critisme/advise, because it can all be used to improve this defense.

gmaxwell:

"It doesn't sound legitimate at all.
It sounds like the writing of someone...
Who doesn't even have a basic understanding of the problem space."

Heres a serious Dev pointing out...
The paper was a Promo Piece designed to give a false sense of security to GoldCoin owners...
And the last thing on earth we need is "help" from a bunch of Promoters.
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October 12, 2013, 06:28:06 PM
 #20

Heres a serious Dev pointing out...

Gmaxwell can be wrong, he is a human. Everyone here should use their own brain. Let's continue the discussion.
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