Cheap way to attack blockchain | Bitcointalksearch.org

BlockSense

newbie

Activity: 14

Merit: 0

Quote from: basil00 on December 02, 2015, 12:03:04 AM

This attack can be made more effective by exploiting this. That is, instead of a vanilla OP_RETURN you use the script:

Code:

    OP_RETURN OP_CHECKMULTISIG

This counts as a extra 20 sigOps. This bug is fixed in 0.12.0 (by making this script non-standard).

Will have a read of this.

oakpacific

hero member

Activity: 784

Merit: 1000

Isn't transaction selection already a NP-hard knapsack problem? What kind of a beast it will become if we throw....computational complexity itself into the mix? "Hmmm, let me estimate if I am gonna spend more time processing these transactions or more time doing the estimation..." Roll Eyes

amaclin

legendary

Activity: 1260

Merit: 1019

Quote from: sidwaltdo on December 16, 2015, 11:00:01 PM

WOW,The day bitcoin starts blacklisting will be the end.

https://gitlab.com/bitcoin/luke-jr-bitcoin/commit/5f8e7180c4b34d5f46c61a6dd2242f4249b5f79a

DuddlyDoRight

sr. member

Activity: 318

Merit: 260

Quote from: sidwaltdo on December 16, 2015, 11:00:01 PM

WOW,The day bitcoin starts blacklisting will be the end.

Never blacklist. Just whitelist. I'm not sure why basic reputation scares people here so bad..

There is nothing built in to the block-chain that says a bank is a bank and again, BTC is a currency not a profit system..

sidwaltdo

newbie

Activity: 1

Merit: 0

WOW,The day bitcoin starts blacklisting will be the end.

DuddlyDoRight

sr. member

Activity: 318

Merit: 260

Problem is fees are already arbritrary creating usability issues.. Add more add more problems..

Oh cool I just put my savings in to bitcoin!! Hey what happen to 0.005% of it or why does it get no confirmations.. No refunds wtf?

Bitcoin is suppose to be a currency not a quick-profit-scheme for people who buy the hardware or learn the internals..

hetecon

full member

Activity: 462

Merit: 100

Viarium.io - DECENTRALIZED VR WORLD

Quote from: basil00 on December 02, 2015, 12:03:04 AM

This attack can be made more effective by exploiting this. That is, instead of a vanilla OP_RETURN you use the script:

Code:

    OP_RETURN OP_CHECKMULTISIG

This counts as a extra 20 sigOps. This bug is fixed in 0.12.0 (by making this script non-standard).

interesting thing to see here. i trying to get this script lang down lol

basil00

member

Activity: 60

Merit: 10

This attack can be made more effective by exploiting this. That is, instead of a vanilla OP_RETURN you use the script:

Code:

    OP_RETURN OP_CHECKMULTISIG

This counts as a extra 20 sigOps. This bug is fixed in 0.12.0 (by making this script non-standard).

mezzomix

legendary

Activity: 2618

Merit: 1252

Quote from: amaclin on December 01, 2015, 02:21:22 PM

Quote from: hetecon on December 01, 2015, 01:47:44 PM

Do you have a github commit for me to look at?

this link have been posted a number of times in this topic
https://github.com/bitcoin/bitcoin/pull/7081

I use a hard coded limit but this pull request will be more flexible.

hetecon

full member

Activity: 462

Merit: 100

Viarium.io - DECENTRALIZED VR WORLD

Quote from: amaclin on December 01, 2015, 02:21:22 PM

Quote from: hetecon on December 01, 2015, 01:47:44 PM

Do you have a github commit for me to look at?

this link have been posted a number of times in this topic
https://github.com/bitcoin/bitcoin/pull/7081

much simpler then expected :0

amaclin

legendary

Activity: 1260

Merit: 1019

Quote from: hetecon on December 01, 2015, 01:47:44 PM

Do you have a github commit for me to look at?

this link have been posted a number of times in this topic
https://github.com/bitcoin/bitcoin/pull/7081

hetecon

full member

Activity: 462

Merit: 100

Viarium.io - DECENTRALIZED VR WORLD

Quote from: mezzomix on December 01, 2015, 01:45:31 PM

It's not limited to the miners. I operate several relay nodes and patched my nodes to reject those transactions before they are stored in the mempool. With this change my nodes no longer forward transactions with a high number of SIGOPS.

With a mining node I would not reject those transactions but require a high fee.

Do you have a github commit for me to look at?

mezzomix

legendary

Activity: 2618

Merit: 1252

It's not limited to the miners. I operate several relay nodes and patched my nodes to reject those transactions before they are stored in the mempool. With this change my nodes no longer forward transactions with a high number of SIGOPS.

With a mining node I would not reject those transactions but require a high fee.

hetecon

full member

Activity: 462

Merit: 100

Viarium.io - DECENTRALIZED VR WORLD

Quote from: mezzomix on December 01, 2015, 02:51:52 AM

Quote from: hetecon on November 30, 2015, 05:23:31 PM

So this will be able to have a fix but requires convincing of the largest pools.

Yes. Miners are able to immediately require higher fees for these transactions or to ignore these transactions when they create blocks.

To me this means it is not a problem with bitcoin concept, but a problem with certain versions of the wallet/mining wallet systems.

mezzomix

legendary

Activity: 2618

Merit: 1252

Quote from: hetecon on November 30, 2015, 05:23:31 PM

So this will be able to have a fix but requires convincing of the largest pools.

Yes. Miners are able to immediately require higher fees for these transactions or to ignore these transactions when they create blocks.

Syke

legendary

Activity: 3878

Merit: 1193

Quote from: basil00 on November 30, 2015, 11:23:47 PM

This specific attack can also be mitigated by enforcing a bytes-per-sigop limit (policy change), as was merged into 0.12.0. Any miner that does not adopt this policy will still be vulnerable.

A fee per sigop sounds like a good plan too.

basil00

member

Activity: 60

Merit: 10

Quote from: hetecon on November 30, 2015, 12:39:36 PM

Is fixing of this issue requiring a full 'hard forking'

Fixing the broken sigOp counting method is indeed a hardfork. It can be fixed when (if?) there is a block-size hardfork, e.g. this is one proposal.

This specific attack can also be mitigated by enforcing a bytes-per-sigop limit (policy change), as was merged into 0.12.0. Any miner that does not adopt this policy will still be vulnerable.

hetecon

full member

Activity: 462

Merit: 100

Viarium.io - DECENTRALIZED VR WORLD