<p>With 51% of the network hashrate the forking attack is theoretically possible. Classically, what you have described is a double spending attack.</p>

<p>First, the attacker pays M->B and B releases the goods. Then, the attacker presents a longer valid chain paying M->M instead and the blocks containing M->B are orphaned.</p>

<p>It is not simply a matter of presenting an alternate block, it must be a valid alternate block(s) with more valid proof of work (a longer chain) which must also be based on the genesis block and any (each) checkpoint.</p>

<p>With 51% of the network hashpower, selfish mining is also possible, where the attacker ignores any network generated blocks and continues to extend their own chain with blocks that they have created. Because the attacker's hashpower is greater, theirs will be the longest chain with the greatest PoW.</p>

CC BY-SA 4.0
2018-05-20T21:34:38.577Z
2018-05-20T21:34:38.577Z
Willtech
<p>I am a student who studies block-chain for these days.</p>

<p>I have a question about forking attack and selfish mining in mining strategies </p>

<p>as you see picture below</p>

<p><a href="https://i.sstatic.net/j9i5h.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/j9i5h.png" alt="enter image description here"></a></p>

<p>I don't understand why miner should send some money to a victim to do forking attack...</p>

<p>what does this means to do forking attack? </p>

<p>is it possible to do forking attack except sending some money to a victim?</p>

<p>and as below picture about selfish mining </p>

<p><a href="https://i.sstatic.net/LiiXP.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/LiiXP.png" alt="enter image description here"></a></p>

<p>what is difference between forking attack and selfish mining if miners exclude </p>

<p>to do send some money to a victim in forking attack?</p>

<p>can anyone help me to understand what M->B and M->M'(double spending) means??</p>

<p>and why do need it to do forking attack??</p>

<blockchain><blockchain-fork><selfish-mining>
what is forking attack? and different between forking attack and selfish mining?
grenier
# what is forking attack? and different between forking attack and selfish mining?

(Asked by: username_0 on 2018-05-20)

I am a student who studies block-chain for these days.

I have a question about forking attack and selfish mining in mining strategies

as you see picture below

[![enter image description here](https://i.sstatic.net/j9i5h.png)](https://i.sstatic.net/j9i5h.png)

I don't understand why miner should send some money to a victim to do forking attack...

what does this means to do forking attack?

is it possible to do forking attack except sending some money to a victim?

and as below picture about selfish mining

[![enter image description here](https://i.sstatic.net/LiiXP.png)](https://i.sstatic.net/LiiXP.png)

what is difference between forking attack and selfish mining if miners exclude

to do send some money to a victim in forking attack?

can anyone help me to understand what M->B and M->M'(double spending) means??

and why do need it to do forking attack??

**Tags:** blockchain, blockchain-fork, selfish-mining


---

## 1 answers

### Answer by username_1 on 2018-05-20. Score: 2

With 51% of the network hashrate the forking attack is theoretically possible. Classically, what you have described is a double spending attack.

First, the attacker pays M->B and B releases the goods. Then, the attacker presents a longer valid chain paying M->M instead and the blocks containing M->B are orphaned.

It is not simply a matter of presenting an alternate block, it must be a valid alternate block(s) with more valid proof of work (a longer chain) which must also be based on the genesis block and any (each) checkpoint.

With 51% of the network hashpower, selfish mining is also possible, where the attacker ignores any network generated blocks and continues to extend their own chain with blocks that they have created. Because the attacker's hashpower is greater, theirs will be the longest chain with the greatest PoW.


---

