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markm

legendary

Activity: 2940

Merit: 1090

Quote from: kalus on April 01, 2014, 12:57:46 AM

Quote from: markm on March 31, 2014, 11:38:41 PM

I just woke up, or maybe still mostly asleep, so maybe my orders of magnitude are off or something but... one gigahash? Isn't that kind of puny to even be considered an attack at all? How the heck is any chain so pathetic that one gigahash is even hardly noticed let alone a threat?

-MarkM-

wouldn't an attacker working on an attack chain be benefiting from low difficulty while mining future blocks? i would have thought TW meant KGW coins could be forked with far less than 51%.

That part puzzles me.

On the one hand, Math claimed that to defend takes significantly more hash power than the attacker.

On the other hand, I thought the "length" of a chain is the total work, so that regardless of whether the work was done in a TARDIS or not it still takes more work than any other fork in order to be the main/real fork?

If the defenders do more work than the attacker, how is the attacker winning with less work? Or do they somehow get more work out of less hashes?

-MarkM-

Nite69

sr. member

Activity: 477

Merit: 500

Quote from: molecular on April 01, 2014, 12:43:43 AM

Thank you!

What would be potential drawbacks / sideeffects of this fix?

There's something I don't quite get... If the attacks works roughly like you explained (quoted here: https://bitcointalksearch.org/topic/m.5582049), then why would we see any effects (as BCX says: "increasingly uneven block times"). After all, BCX only publishes his secret chain at the end of the attack, not at this point, right?

I would appreciate others to comment on this: does it fix the problem? Does it have any unwanted side-effects? I have not found, but that does not mean there are no.

I'm wondering the same; there should ne no side effects before the secret attack chain is published.

Not sure if I should publish this or not. However, I think if someone is anyway doing it, then publishing this should be just good on the long run. And you cannot know if my fix works or not, if you don't know what it should fix.

This is one way of using the TW vulnerability, which that code prevents (but not the earlier fix):

1. Use isolated mining environment, as you need at this kind of attack
2. First generate blocks with long timestamps to get low diff on your own chain. This takes time, but gets easier after every block.
3. When you have a low difficulty, start generating blocks with time differences (hours:minutes) : +12:00, -11.51, +12.00 -11.51... This is for 5 minute target times

at step 3, you can generate 2 blocks every 9 minutes with a very low difficulty. Eventually, your chain is longer than the official, and you can publish it.

Every time you generate a block with +12:00, you get -10% difficulty. Every time you generate -11:51, you get +10%, ie you stay at the low difficulty. The problem is that KGW difficulty calculation counts from the latest block's time, not the latest blocktime

But note; this is also prevented with automatic checkpoints. And you have to start over after every published checkpoint.

kalus

sr. member

Activity: 420

Merit: 263

let's make a deal.

Quote from: markm on March 31, 2014, 11:38:41 PM

I just woke up, or maybe still mostly asleep, so maybe my orders of magnitude are off or something but... one gigahash? Isn't that kind of puny to even be considered an attack at all? How the heck is any chain so pathetic that one gigahash is even hardly noticed let alone a threat?

-MarkM-

wouldn't an attacker working on an attack chain be benefiting from low difficulty while mining future blocks? i would have thought TW meant KGW coins could be forked with far less than 51%.

illodin

hero member

Activity: 966

Merit: 1003

Quote from: markm on March 31, 2014, 11:38:41 PM

I just woke up

lol... your only weakness truly is hungry and sleepy. Cheesy

molecular

donator

Activity: 2772

Merit: 1019

Quote from: Nite69 on March 31, 2014, 10:40:06 PM

Quote from: ?? on ??

Actually mikey you might want to ask Nite69, the developer brought on by the Auroracoin team to help prepare the KGW TW fix. Nite69 realizes there is a KGW TW underway and by extension so does the Auroracoin Team even though won't and can't admit it.

About the vulnerability BCX found; I'm quite sure this will fix it, like any time warp vulnerability. Shame us, we should have fixed this already earlier Undecided

Code:

+	int64 LatestBlockTime = BlockLastSolved->GetBlockTime();
 	for (unsigned int i = 1; BlockReading && BlockReading->nHeight > 0; i++) {
 		if (PastBlocksMax > 0 && i > PastBlocksMax) { break; }
 		PastBlocksMass++;
@@ -894,8 +895,10 @@ unsigned int static GravityWell(const CBlockIndex* pindexLast, const CBlock *pbl
 		if (i == 1)	{ PastDifficultyAverage.SetCompact(BlockReading->nBits); }
 		else		{ PastDifficultyAverage = ((CBigNum().SetCompact(BlockReading->nBits) - PastDifficultyAverage
Prev) / i) + PastDifficultyAveragePrev; }
 		PastDifficultyAveragePrev = PastDifficultyAverage;
-		
-		PastRateActualSeconds			= BlockLastSolved->GetBlockTime() - BlockReading->GetBlockTime();
+		if (LatestBlockTime < BlockReading->GetBlockTime()) {
+			LatestBlockTime = BlockReading->GetBlockTime();
+		}
+		PastRateActualSeconds			= LatestBlockTime - BlockReading->GetBlockTime();
 		PastRateTargetSeconds			= TargetBlocksSpacingSeconds * PastBlocksMass;
 		PastRateAdjustmentRatio			= double(1);
 		if (PastRateActualSeconds < 0) { PastRateActualSeconds = 0; }

Thank you for finding this and bringing this to general knowledge, however, I would prefer some other way to show it..

Thank you!

What would be potential drawbacks / sideeffects of this fix?

There's something I don't quite get... If the attacks works roughly like you explained (quoted here: https://bitcointalksearch.org/topic/m.5582049), then why would we see any effects (as BCX says: "increasingly uneven block times"). After all, BCX only publishes his secret chain at the end of the attack, not at this point, right?

markm

legendary

Activity: 2940

Merit: 1090

I just woke up, or maybe still mostly asleep, so maybe my orders of magnitude are off or something but... one gigahash? Isn't that kind of puny to even be considered an attack at all? How the heck is any chain so pathetic that one gigahash is even hardly noticed let alone a threat?

-MarkM-

micryon

full member

Activity: 154

Merit: 100

Quote from: Nite69 on March 31, 2014, 10:40:06 PM

Quote from: ?? on ??

Actually mikey you might want to ask Nite69, the developer brought on by the Auroracoin team to help prepare the KGW TW fix. Nite69 realizes there is a KGW TW underway and by extension so does the Auroracoin Team even though won't and can't admit it.

About the vulnerability BCX found; I'm quite sure this will fix it, like any time warp vulnerability. Shame us, we should have fixed this already earlier Undecided

Code:

+	int64 LatestBlockTime = BlockLastSolved->GetBlockTime();
 	for (unsigned int i = 1; BlockReading && BlockReading->nHeight > 0; i++) {
 		if (PastBlocksMax > 0 && i > PastBlocksMax) { break; }
 		PastBlocksMass++;
@@ -894,8 +895,10 @@ unsigned int static GravityWell(const CBlockIndex* pindexLast, const CBlock *pbl
 		if (i == 1)	{ PastDifficultyAverage.SetCompact(BlockReading->nBits); }
 		else		{ PastDifficultyAverage = ((CBigNum().SetCompact(BlockReading->nBits) - PastDifficultyAverage
Prev) / i) + PastDifficultyAveragePrev; }
 		PastDifficultyAveragePrev = PastDifficultyAverage;
-		
-		PastRateActualSeconds			= BlockLastSolved->GetBlockTime() - BlockReading->GetBlockTime();
+		if (LatestBlockTime < BlockReading->GetBlockTime()) {
+			LatestBlockTime = BlockReading->GetBlockTime();
+		}
+		PastRateActualSeconds			= LatestBlockTime - BlockReading->GetBlockTime();
 		PastRateTargetSeconds			= TargetBlocksSpacingSeconds * PastBlocksMass;
 		PastRateAdjustmentRatio			= double(1);
 		if (PastRateActualSeconds < 0) { PastRateActualSeconds = 0; }

Thank you for finding this and bringing this to general knowledge, however, I would prefer some other way to show it..

wow... well that's quite simple

btw looks like balduro has also been adding static checkpoints, as an additional countermeasure... https://github.com/baldurodinsson/auroracoin-project/commits/master

Nite69

sr. member

Activity: 477

Merit: 500

Quote from: ?? on ??

Actually mikey you might want to ask Nite69, the developer brought on by the Auroracoin team to help prepare the KGW TW fix. Nite69 realizes there is a KGW TW underway and by extension so does the Auroracoin Team even though won't and can't admit it.

About the vulnerability BCX found; I'm quite sure this will fix it, like any time warp vulnerability. Shame us, we should have fixed this already earlier Undecided

Code:

+	int64 LatestBlockTime = BlockLastSolved->GetBlockTime();
 	for (unsigned int i = 1; BlockReading && BlockReading->nHeight > 0; i++) {
 		if (PastBlocksMax > 0 && i > PastBlocksMax) { break; }
 		PastBlocksMass++;
@@ -894,8 +895,10 @@ unsigned int static GravityWell(const CBlockIndex* pindexLast, const CBlock *pbl
 		if (i == 1)	{ PastDifficultyAverage.SetCompact(BlockReading->nBits); }
 		else		{ PastDifficultyAverage = ((CBigNum().SetCompact(BlockReading->nBits) - PastDifficultyAverage
Prev) / i) + PastDifficultyAveragePrev; }
 		PastDifficultyAveragePrev = PastDifficultyAverage;
-		
-		PastRateActualSeconds			= BlockLastSolved->GetBlockTime() - BlockReading->GetBlockTime();
+		if (LatestBlockTime < BlockReading->GetBlockTime()) {
+			LatestBlockTime = BlockReading->GetBlockTime();
+		}
+		PastRateActualSeconds			= LatestBlockTime - BlockReading->GetBlockTime();
 		PastRateTargetSeconds			= TargetBlocksSpacingSeconds * PastBlocksMass;
 		PastRateAdjustmentRatio			= double(1);
 		if (PastRateActualSeconds < 0) { PastRateActualSeconds = 0; }

Thank you for finding this and bringing this to general knowledge, however, I would prefer some other way to show it..

Starlightbreaker

legendary

Activity: 1764

Merit: 1006

Quote from: illodin on March 31, 2014, 01:53:21 PM

Quote from: Starlightbreaker on March 31, 2014, 09:56:16 AM

Quote from: illodin on March 31, 2014, 06:15:01 AM

Quote from: Starlightbreaker on March 31, 2014, 01:33:42 AM

Quote from: illodin on March 30, 2014, 09:53:22 PM

Quote from: Starlightbreaker on March 29, 2014, 11:31:15 PM

so when can we expect fireworks from you?

go fuck something up, need some entertainment here. Angry

You sound like you missed the best money making opportunity of the year so far.

sorry, i rode AUR's pump and dump.

in at 0.03, out at 0.11, unlike idiots that end up as bagholders.

Grin

Tempted to post a screenshot of my wallet solomining AUR at start but don't want anymore idiots crying realizing 3x profit wasn't actually the "opportunity of the year".

Grin

hmm, i think i missed a zero somewhere...i'm pretty sure it was around 28-30x gain during that period.

Well don't be shy, let's just say 300x?

Hah, i wish it was 300x.

digitalindustry

hero member

Activity: 798

Merit: 1000

‘Try to be nice’

Looks like AUR is an unmitigated success.

It only gets harder from here on in for the monopoly capitalists. Think about it there is next to zero infustructure on ground right now, yet price is still sky high compared to take up.

digitalindustry

hero member

Activity: 798

Merit: 1000

‘Try to be nice’

Quote from: kewal on March 31, 2014, 03:15:05 PM

This is a great example of why alt-coins should be implemented on top of a system like Ethereum. A small group can have a coin, and be protected by the overall use and mining power behind the much larger community. I'm looking forward to the pre-sale of Ether.

Ha ha ha good one.

At least someone has a sense of humor in this circle jerk.

micryon

full member

Activity: 154

Merit: 100

Quote from: nbk on March 31, 2014, 04:14:23 PM

part of the guide....

Quote

For large adjustment factors this happens earlier than for the ones closer to one. This is to have a quick adaptation if the hashrate changes a lot, and a slower one if not - then we want a longer period to get a better average. The parameters of the Kimoto formula are adjusted in such a way that one roughly adjusts in one day to a 10% change and in seven days to a 1.2% change. A minimum of 144 blocks determine the new difficulty and at most 4032 (0.25 days or 7 days for a 2.5 minute blocktime).

What happens when the minimum of 144 blocks isn't reached or the maximum of 4032 blocks is exceeded?

The minimum is 144 blocks. So if the adjustment factor is larger than 1+0.7084, then the factor for 144 blocks is taken. At 4032 the algo stops and the average for 4032 is taken no matter what. KGW gives an answer for both boundary cases.

The adjustment ratio may do a little to curb it.. but fundamentally the problem is in this segment:

Code:

PastRateActualSeconds                        = BlockLastSolved->GetBlockTime() - BlockReading->GetBlockTime();

Code:

if (PastRateActualSeconds != 0 && PastRateTargetSeconds != 0) {
                bnNew *= PastRateActualSeconds;
                bnNew /= PastRateTargetSeconds;

bnNew being the current difficulty.

Because of this you can continually trick the algo to lower the difficulty down to:

Code:

bnProofOfWorkLimit(~uint256(0) >> 20);

You have to imagine just mining outside of real network, in your own intranet.. with just two computers. and then flipping the system time to the future, making algo believe that more time has passed than actually has between blocks.

nbk

member

Activity: 132

Merit: 10

MEGACOIN

part of the guide....

Quote

For large adjustment factors this happens earlier than for the ones closer to one. This is to have a quick adaptation if the hashrate changes a lot, and a slower one if not - then we want a longer period to get a better average. The parameters of the Kimoto formula are adjusted in such a way that one roughly adjusts in one day to a 10% change and in seven days to a 1.2% change. A minimum of 144 blocks determine the new difficulty and at most 4032 (0.25 days or 7 days for a 2.5 minute blocktime).

What happens when the minimum of 144 blocks isn't reached or the maximum of 4032 blocks is exceeded?

The minimum is 144 blocks. So if the adjustment factor is larger than 1+0.7084, then the factor for 144 blocks is taken. At 4032 the algo stops and the average for 4032 is taken no matter what. KGW gives an answer for both boundary cases.

micryon

full member

Activity: 154

Merit: 100

Quote from: nbk on March 31, 2014, 03:48:56 PM

Quote

Essentially KGW just makes it easier to pull off a 51% attack, since it retargets every block using timestamps.

and what about KGWs longtime adjustment?

do you set different parameter to your KGW?

I'm not sure exactly what you mean by longtime adjustment, do you mean the adjustment ratio?

Code:

  PastRateAdjustmentRatio                        = double(PastRateTargetSeconds) / double(PastRateActualSeconds);

What I'm referring to the vulnerability is really just this:

Code:

  PastRateActualSeconds                        = BlockLastSolved->GetBlockTime() - BlockReading->GetBlockTime();

Which basically reads system clocks... and feeds into the ratio adjustment that is used to calc the next diff..

Hirocoin's code will basically just prevent acceptance of a publishing of a bad time-warped private chain, by checking against timestamps before accepting blocks, limiting the warping factor.

Code:

if (GetBlockTime() > GetAdjustedTime() + 15 * 60) {
           return error("AcceptBlock() : block's timestamp too far in the future");
        }

nbk

member

Activity: 132

Merit: 10

MEGACOIN

Quote

Essentially KGW just makes it easier to pull off a 51% attack, since it retargets every block using timestamps.

and what about KGWs longtime adjustment?

do you set different parameter to your KGW?

micryon

full member

Activity: 154

Merit: 100

After integrating KGW into my own coins code.. I can see how KGW does open up an additional vulnerability of a preexisting timewarp attack/51% attack vector as described succinctly here: https://litecoin.info/Time_warp_attack

Essentially KGW just makes it easier to pull off a 51% attack, since it retargets every block using timestamps.

But it's not that easy to begin with to pull that off, and will require some special coding of a secret chain-client to do the private chain mining to be in perfect unison and publish blocks at the right time. Not like anyone with 51% hash power just throwing at a pool will be able to pull it off... And for anyone to really bother, it has to really be worth their while... (or they are just really interested in an academic experiment)

So it's not as easy to execute the attack as people here think... and the "damage" is far less than what people think as well. So it's not "game-over" even if it does happen, it can be repaired.

I took Hirocoin's change recently into my own coin to make it a bit harder to execute.. doesn't make it impossible.. but it's just more barriers: https://github.com/micryon/planetdollar/commit/0c3e5f2acefc77d34ac60e272ab662b6a3120366

molecular

donator

Activity: 2772

Merit: 1019

Quote from: smoothie on March 31, 2014, 05:19:43 AM

oh this is like the good ole days.

Not secure the network and get PWNED.

the good old times?

kewal

newbie

Activity: 5

Merit: 0

This is a great example of why alt-coins should be implemented on top of a system like Ethereum. A small group can have a coin, and be protected by the overall use and mining power behind the much larger community. I'm looking forward to the pre-sale of Ether.

nbk

member

Activity: 132

Merit: 10

MEGACOIN

for weeks i red this timewarp shit...everyone is hating at aurora, kgw, kimoto & megacoin....
so has anyone of these professionals red the kimoto gravity well guide?
here you find it!!! http://imgur.com/a/z2AIw

poornamelessme

hero member

Activity: 1204

Merit: 509

Quote from: _noname_ on March 31, 2014, 02:22:38 PM

Following the deletion of my message by the scammer (BCX)

I have created a scam accusation thread in corresponding forum

https://bitcointalksearch.org/topic/scam-accusation-message-deleted-by-scammer-551875

One of my posts was deleted in one of his self-moderated threads, as well. Although BCX claimed he didn't delete it, and let me repost. He's actually been pretty good with allowing most comments in his threads ... although I guess he might draw the line at people calling him a scammer, I guess.

As for this forum, when I first started here, I assumed it was like any other forum. Quickly I found that not to be the case. Forum moderation is close to nil.

So we get tons of trolling, fud, false information, shill accounts, etc. And I expect it won't be fixed, as this little alt section is looked down upon by whomever owns this forum. It's a weird situation, especially for those new here. I just sort of take it for what it is... more or less a hunt for real info, while trying to ignore all the garbage.

Topic: delete - page 2. (Read 113461 times)