user1878: Suppose it was possible to influence a miner to create many forks.  My understanding is that a miner won't retransmit the fork, but will track it internally.

Where is this information saved in a miner (disk, RAM, etc)?
What protections exist to protect a miner from a resource depletion attack due to forking?


user153: A valid block that is orphaned is just as expensive to create as a block on top of the longest chain.  
It makes no economic sense to create a block that has almost no chance of becoming the longest chain.  Today, that costs maybe $500 per block for electricity and amortized capital to solve a block.  And to DDoS you would need many many blocks, so you'ld likely be expending millions of dollars before any developers would even need to start worrying about mitigation, if there were truly a problem.
[Edit: Also see ThePiachu's comment about the checkpoint protecting against new forks emerging for blocks back when there was a low difficulty.]

user323: If you mean a miner as in a computer that only does mining, it should be generally as resistant to DOS attacks as any casual computer on the network - it doesn't open its ports.
If you are worried about a standard client being flooded with many blocks and having to store it - the developers did think of that and they put in the checkpoint system. Basically, making a lot of forks of the new blocks would require a lot of computational power and so forth, so it is highly unlikely. However, changing some of the earliest blocks in existence would be dirt cheap nowadays. However, the standard client will not accept any block chain forks that branch out from blocks older than the most recent checkpoint.

1878: <p>Suppose it was possible to influence a miner to create many forks.  My understanding is that a miner <a href="https://bitcoin.stackexchange.com/a/3132/1878">won't retransmit the fork, but will track it internally</a>.</p>

<ul>
<li><p>Where is this information saved in a miner (disk, RAM, etc)?</p></li>
<li><p>What protections exist to protect a miner from a resource depletion attack due to forking?</p></li>
</ul>
 153: <p>A valid block that is orphaned is just as expensive to create as a block on top of the longest chain.  </p>

<p>It makes no economic sense to create a block that has almost no chance of becoming the longest chain.  Today, that costs maybe $500 per block for electricity and amortized capital to solve a block.  And to DDoS you would need many many blocks, so you'ld likely be expending millions of dollars before any developers would even need to start worrying about mitigation, if there were truly a problem.</p>

<p>[Edit: Also see ThePiachu's comment about the checkpoint protecting against new forks emerging for blocks back when there was a low difficulty.]</p>
 323: <p>If you mean a miner as in a computer that only does mining, it should be generally as resistant to DOS attacks as any casual computer on the network - it doesn't open its ports.</p>

<p>If you are worried about a standard client being flooded with many blocks and having to store it - the developers did think of that and they put in the checkpoint system. Basically, making a lot of forks of the new blocks would require a lot of computational power and so forth, so it is highly unlikely. However, changing some of the earliest blocks in existence would be dirt cheap nowadays. However, the standard client will not accept any block chain forks that branch out from blocks older than the most recent checkpoint.</p>
