<p>I am currently studying for the CS251 Cryptocurrencies and Blockchain Technologies exam. In a past exam, there is this question without an answer and I would really appreciate your help so that I can better understand it:</p>
<p><em>Recall that a selfish miner temporarily refrains from publishing mined blocks in an
effort to get several blocks ahead of other miners, thereby causing other miners to
waste effort mining orphan blocks. When a selfish miner is only one block S ahead of
the public chain, if another miner mines and publishes a block O at the same height as
S, the selfish miner immediately publishes S. Let γ be the probability that, when this
happens, an honest miner will try to mine the next block on S instead of on O.</em></p>
<p><em>A) How can an attacker ensure that γ ≈ 1 (in other words, S almost always overrides O) on today’s Bitcoin network?</em></p>
<p>Thank you very much in advance for your help!</p>

CC BY-SA 4.0
2021-07-29T16:45:05.727Z
A guess: what if the selfish miner deliberately omits from S a number of high-fee transactions that are in O?  Then other miners have an incentive to mine on S, because then they can claim the fees of those transactions, whereas with O they could not.
Nate Eldredge
CC BY-SA 4.0
2021-07-29T19:44:24.667Z
@NateEldredge That's a good one! I would not have thought of that.
bigjosh
CC BY-SA 4.0
2021-07-30T08:49:27.813Z
@NateEldredge thanks! So you mean the selfish miner omits the high transaction fee transactions so that miners have the chance to get a block with them for the next block?
Python-Data-Science-Learner
CC BY-SA 4.0
2021-07-30T12:21:17.040Z
@Python-Data-Science-Learner: Right.  But I don't know if that's what your exam has in mind.  I also don't know whether your exam would consider a miner "honest" who would  mine on S instead of O to get more fees, despite having seen O first.
Nate Eldredge
<attack><selfish-mining>
Selfish mining attack: Probability of block being mined - CS251 exam question
Python-Data-Science-Learner
# Selfish mining attack: Probability of block being mined - CS251 exam question

(Asked by: username_0 on 2021-07-29)

I am currently studying for the CS251 Cryptocurrencies and Blockchain Technologies exam. In a past exam, there is this question without an answer and I would really appreciate your help so that I can better understand it:

*Recall that a selfish miner temporarily refrains from publishing mined blocks in an
effort to get several blocks ahead of other miners, thereby causing other miners to
waste effort mining orphan blocks. When a selfish miner is only one block S ahead of
the public chain, if another miner mines and publishes a block O at the same height as
S, the selfish miner immediately publishes S. Let γ be the probability that, when this
happens, an honest miner will try to mine the next block on S instead of on O.*

*A) How can an attacker ensure that γ ≈ 1 (in other words, S almost always overrides O) on today’s Bitcoin network?*

Thank you very much in advance for your help!

**Tags:** attack, selfish-mining

> **Comments:**
> **username_1**: A guess: what if the selfish miner deliberately omits from S a number of high-fee transactions that are in O?  Then other miners have an incentive to mine on S, because then they can claim the fees of those transactions, whereas with O they could not.  
> **username_2**: @NateEldredge That's a good one! I would not have thought of that.  
> **username_0**: @NateEldredge thanks! So you mean the selfish miner omits the high transaction fee transactions so that miners have the chance to get a block with them for the next block?  
> **username_1**: @username_0: Right.  But I don't know if that's what your exam has in mind.  I also don't know whether your exam would consider a miner "honest" who would  mine on S instead of O to get more fees, despite having seen O first.  

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