Topic: The Biggest Flaw with Bitcoin that Could Crash the Entire System (Read 5350 times)

In reality nobody is going to accept a fork that causes >100 block reorg, which is what it would take for that attack to work.

At best you cause a severe temporary disruption until the network adapts.

Sure you're mining blocks but you're not spending coins you don't own like you stated. 

Even if you have 51% hash rate, it only means you can be a little bit faster than others. You cannot revert the block chain too much. Otherwise, you need a long time to catch up with the normal chain, and by that time you may already lose the 51% advantage because of the difficulty adjustment.

For example, if you have 60% network hash rate, and you decide to quit the main chain and create a new chain. At the current difficulty, you can generate 1.5 times faster than all other miners. Say you begin this exactly in the beginning of the difficulty change cycle, and you have to get more blocks than the original chain before the difficulty changes. Otherwise, the difficulty of main chain adjusts and you lose your advantage. That means you have to generate more blocks before next 2016 blocks. In this period, you can generate 2016 * 1.5 = 3024 blocks. So you can only revert the blockchain by around 1000 blocks if you have 60% network hashing rate.

If you have only 51%, then you are only 1.04 times faster. You can only generate 2096 blocks in this period, so you can only revert 80 blocks back at most.

Moreover, each new release of bitcoin client will hardcode the recent block hash, so no one can revert beyond this point. Therefore, if you cannot catch up before a new official client release, you lose all your efforts.

Finally, all this reverting only causes one result: bitcoin becomes zero value and will not bring any profit to the attacker, because everyone will notice if you revert the blockchain by only a couple of blocks. So the attacker lose all the value of bitcoins they have, and moreover they have lost the chance to earn more than 2000 BTC (>1 million dolloar)  per day forever. Therefore, 51 attack is only meaningful to the organizations who want to destroy bitcoin at any cost.


Besides, what you described has nothing to do with spending others' coins.

Any transaction has to be signed by the owner's private key, so no matter how powerful your miner is, you cannot spend anyone's bitcoin without get the private key first.

It is not as easy as you make it sound.

It is not the same to change the last, current or next block than to change a given block in the past. Even if you've broken the encryption there's still a LOT more work involved.

I never stated it, directly or indirectly. Nah you must not break it

It is so easy and yes it is possible: just rewrite the chain from when these coins were mined. You will find the blocks, so you will have mined them, so they will be your. Thus, the other transactions never existed. That is how a 51% attack work, you can rewrite the chain as you wish.
No need to break ECDSA. You just make it so you mined these coins. So you own them. 51% attack.

Gabi, please tell me how it's possible to spend coins you don't own.  It isn't possible.  Unless you actually think that reversing a transaction is actually your victim sending coins back you you?

It's just not the way it works.

You stated so indirectly. In order to steal coins from most transactions, ECDSA must be broken.

Where did i exactly claimed that? Please point me to that  Because i never said that  I just said the attacker can spend coins owned by other people 

Are you claiming that somebody broke ECDSA?

Yes we should. Because it is wrong.

The attacker CAN do these things.

Hmmm , we should correct the bitcopedia then?

The attacker can't:
Reverse other people's transactions
Prevent transactions from being sent at all (they'll show as 0/unconfirmed)
Change the number of coins generated per block
Create coins out of thin air
Send coins that never belonged to him

Easier than just printing money? Than creating money? Nah

Only if you assume they cannot profit from BTC, which would in fact be easier for them to do.

False, false, false.

He can steal anyone's bitcoin and yes he can change the blockchain history.

Upset the value? Exactly what banks and governments would like!

So you can easily get mining chips at $40/TH, or $0.04/GH. That's great, I bet you will be billionaire soon. Meanwhile, at the time you get 10 PH, the network hashing rate will definitely already 100 PH.

First, even with 1TH per chip, thousands of chips still are only several PH. You still need to build tens of thousands of chips overnight to get 51% hash rate.
Second, not anyone can have the ability to have the technology, fund, product lines, and meanwhile keep confident for several months.
Third, only countries like USA and China have the ability to do that, but even they really want to kill bitcoin they have much simpler ways.

NSA doesnt have 10nm. No one does. Not that you need it, 28nm would work just fine. ~100TH per wafer, just order a few 100 wafers at less than $4000 each, thats hardly the problem.

anyone can really destroy bitcoin if they want to... seriously. Assuming NSA has 10nm technology and build thousands of miners and dont tell the world. THen  create a new pool instantaneously with 10000000TH.

That will kill off the bitcoin mining straightway.

I believe they have the money, the brains and the capability. Why aren't they doing it?

yawn

PeerCoin solves this, and other pos