Quote from: sor.rge on June 14, 2013, 10:04:17 AM

Quote from: AnonyMint on June 14, 2013, 05:07:19 AM

Incorrect. If my SH controls the transactions in the last TBs for that hash, I can caused the hash to have any value I want (at some cost).

That cost is going to be very high. Bitcoin is built around the hardness of this task, only they try to find a partial preimage, while we're talking about finding a full preimage. So if you can choose the seed here, you'll have no trouble killing bitcoin as well. For some hashes this has not been accomplished even once: https://en.wikipedia.org/wiki/Preimage_attack

You confuse yourself. Bitcoin is a race to compute the next hash solution. There can't be a preimage because every peer is racing to compute it.

Quote from: sor.rge on June 14, 2013, 10:04:17 AM

So you don't get to choose your seed.

This is silly, it's like saying "I got this encrypted message, so I can decrypt it by enumerating the key. So the encryption is useless." Yes you can, go on.
If you still find it difficult to understand, play a little game: imagine the seed is MD5 hash (that's a "weak" one), and the transactions are written in ascii text. The first transaction says "Transfer 5 decrits from account 1 to 2." You choose the next transaction(s), concatenate them with that string and compute the MD5. Now try to have the result of all zeroes. If you succeed, post your transaction here.

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It has deterministic values from every seed. All I have to do is compute from any seed of my choice, target my SH IDs to those values over any length of time that it takes for me to do so. Then just create that hash seed every time one of my SH is last. Thus disruption.

First, the IDs are chosen, and then you know the seed. Not the other way around.

I can choose a seed a priori, run the random generator off that seed, then set my IDs to that seed. Then later when my SH is last, I can add data to the TB to get that seed. Because the random generator is reproducible (deterministic) from any given seed-- there is no entropy added by the random generator.

Geez, that should be obvious to you.

Quote from: sor.rge on June 14, 2013, 10:04:17 AM

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Quote from: sor.rge on June 14, 2013, 12:59:19 AM

In order to prevent that, I proposed fixing all the seeds completely and not using any "entropy" by your terms. While this complicates the attack significantly, it's still not bulletproof.

Then I only need to target those known patterns. I have as much time as I need to get my SH's IDs into that pattern.

Yes. Still it may be very difficult, but it's safer to use the "random" input.

You think, but you don't know what you are thinking. I minored in math. Thus I understand the lack of preimagable entropy to be critical and fundamental.