[p2p-hackers] Error correcting codes to prevent failure in BitTorrent like systems?

[Stelian]

Nick Johnson wrote:

> If we assume there are 4 peers left on the network, each with 50% of
> the file remaining, on average they will be able to reconstruct 50% +
> 25% + 12.5% + 6.25% = 93.75% of the file, which exceeds the threshold
> required to reconstruct with check blocks.

Your concern over the disappearing seed is obviously relevant in case of
a slow seed, otherwise the probability that the seed has not uploaded
all the blocks at least once before departing is practically very low.
So let's assume a slow seed, a seed so slow that once it has finished
uploading a block, all the lechers will share the new available block
instantly among them.
Assuming the seed has time to upload only 90% of the original file, then
it will have time to upload only 81.8% from the new file (10% larger
because of the error correction) - which is of course insufficient to
reconstitute the file, thereby denying the any apparent gain.