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From: "Jonathan Toomim (Toomim Bros)" <j@toom.im>
To: Bitcoin Dev <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Weak block thoughts...
Date: Wed, 23 Sep 2015 15:16:14 -0700	[thread overview]
Message-ID: <03FF5567-DF6E-4242-B63F-D71D1E7E393F@toom.im> (raw)
In-Reply-To: <CABsx9T3NFRO5nw3z=jrs0Hu3caVNkkTTTb1ibqR7LMWsoou9RQ@mail.gmail.com>


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On Sep 23, 2015, at 2:37 PM, Gavin Andresen via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org> wrote:

> Take care, here-- if a scheme is used where e.g. the full solution had
> to be exactly identical to a prior weak block then the result would be
> making mining not progress free because bigger miners would have
> disproportionately more access to the weak/strong one/two punch. I
> think what you're thinking here is okay, but it wasn't clear to me if
> you'd caught that particular potential issue.
> 
> I'm assuming the optimized protocol would be forward-error-coded (e.g. using IBLTs)  and NOT require the full solution (or follow-on weak blocks) to be exactly the same.
> 

One possible improvement on this is to cache Merkle nodes/subtrees. When a weak block is created, nodes could cache the hashes for the Merkle nodes along with each node's children. A miner could then describe their block in terms of Merkle nodes (describing groups of 2^n transactions), which would give them the ability to copy e.g. 87.5% or 96.875% or whatever of their new block from someone else's weak block but with a few modifications (e.g. new transactions) in the remaining non-prespecified portion. This gives small miners the ability to trade off versatility (do I specify all of the transactions with my own Merkle structure?) versus propagation speed (do I copy all of my Merkle tree from another miner's weak block?) with all steps in between.

I've got a proposal for a block propagation protocol inspired by bittorrent applied to the Merkle tree instead of chunks of a file. Weak blocks would fit in with this blocktorrent protocol quite nicely by caching and pre-transmitting Merkle nodes. I don't want to hijack this thread, so I'll post it under a separate subject in an hour or so.

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  reply	other threads:[~2015-09-23 22:27 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-09-23 15:43 [bitcoin-dev] Weak block thoughts Gavin Andresen
2015-09-23 16:07 ` Bryan Bishop
2015-09-23 19:24   ` Gregory Maxwell
2015-09-23 21:37     ` Gavin Andresen
2015-09-23 22:16       ` Jonathan Toomim (Toomim Bros) [this message]
2015-09-24  1:11       ` Rusty Russell
2015-09-27  1:39       ` Gregory Maxwell
2015-09-27  9:42         ` Tier Nolan
2015-09-27 15:10           ` Kalle Rosenbaum
2015-09-27 19:50             ` Gregory Maxwell
2015-09-28  8:30               ` Kalle Rosenbaum
2015-09-28 13:30                 ` Jonathan Toomim (Toomim Bros)
2015-09-23 16:07 ` Btc Drak
2015-09-23 16:28 ` Peter R
2015-09-23 17:40   ` Gavin
2015-09-23 17:49     ` Peter R
2015-09-23 18:48 ` Tier Nolan
2015-09-24  1:32 ` Rusty Russell

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