Topic: High Resolution, Dual-Difficulty Blockchain - page 2. (Read 2512 times)

I believe the only extra work required by miners is that they broadcast blocks that meet the minor block difficulty requirement.  The announced minor blocks only need to build on the last major block (they don't need to build on each other).  Not all of the network will care about minor blocks, but people that want to get a good indicator of the risk associated with accepting a block after a few seconds will care.  The key to this working will be that virtually all miners on the network support it.  If only 10% of the miners support it, then a minor block is not a very good indicator of whether the overall mining network will ultimately validate a given transaction.  This will very likely be a good revenue source for miners…they could charge a fee for notifications of these minor block when they're found.  Other services could aggregate these notifications, charging subscriber fees and passing a portion along to the miners.  The aggregators would provide a single source for these minor block notifications for people that needed a good, fast, reliable transaction risk assessment.  The aggregators would advertise that they represent 87.45% of the bitcoin mining network or some such.  Miners would certainly take advantage as it's an additional revenue opportunity for them.

I´ve thought about multi-level chains before, or even chains with fixed transaction/difficulty ratio for any chosen difficulty. The problem I see is that it´s difficult to predict which will be "Nash equilibrium" of the system or even if an equilibrium exists. Will all miners start making only the lowest difficulty blocks ? Or will they ignore and them always mine the ones with higher rewards?

One possible solution may be to fix the number of low difficulty blocks before a high difficulty block must appear (say in 10:1 ratio). Bit then you will have some (predictable) time intervals where there are no fast confirmations.


Best regard, Sergio.

This is a great idea.  When I think about it, I'm reminded of approaches that mitigate the risk of a 0 confirmation transaction…they basically listen to their peers and if a high degree of peers are reporting that a transaction is valid, then you assume that the risk associated with that transaction is lower…however, that solution treats every node as equal regardless of how much or little mining power might be behind it.  As Casascius points out, p2pool works very much like this…it would be great to continue this line of thinking and get miners (and the pools) to start announcing such "minor blocks" …these don't have to be retained by anyone after a few major blocks have been found…and not every node needs to listen for them or propagate them, but it's a great solution for accepting low value transactions after a few seconds.  *If* the overwhelming majority of mining power on the network supported this, then you would have a much better indicator after just a few seconds regarding the risk of accepting a transaction.  More analysis would be needed, but I'd say it's very likely that the economics are such that for transactions of as much as $100, you could be very safe accepting a transaction after 10 seconds…and for $1000 to $10000, a minute or two would probably push the risk into the realm of insignificance (particularly if it's a transaction between parties that have just a small amount of trust or recourse).

I am interest... mayhap deepbit will be losing a mini-miner. I'll have to look into this when I have a chance.

This already exists today!

It's called P2Pool.

It even follows the very same ten second rule you speak of.

Imagine a Bitcoin fork with the following modification: instead of a single difficulty target, there are two. Let’s call them the major difficulty and the minor difficulty, and let’s posit that the minor difficulty is 60 times easier than the major difficulty.

Miners can hash until they find one of the two targets. If a miner finds a minor difficulty, he broadcasts the block as usual. This is expected to happen approximately every ten seconds. These blocks will be very frothy, because there will likely be more valid blocks broadcast in a cluster of a few seconds. This doesn’t worry us too much (keep reading). Rewards will somehow be proportional to difficulty.

Approximately every ten minutes, a major block is found. Being just like any block, this is the authoritative chain of all the blocks that came before it, including the minor blocks. Since the difficulty is high, this will be the authoritative branch, unless another major block appears at the same time and competes with it. Assuming there's a clear winner, all historical frothiness is resolved, and frothiness begins anew for the next ten minutes.

The advantages of this system are:

* Higher resolution chronology. Bitcoin is a distributed record of chronology, and the original blockchain has a resolution of about 10 minutes. This one will have a resolution of about 10 seconds. This may not be extremely useful for standard transactions, but may be very important for some kinds of transactions, such as betting and stock trading.

* Minor blocks make 0/confirmation type double spending more difficult. Actual 0/confirmation attacks remain the same, but a vendor need only wait ten seconds for a minor block. Gaming the minor blocks would effectively require a 51% attack.

Disadvantages:

* The behavior of the system isn’t well understood. There will likely be many branches of minor blocks between the major blocks, which leads to wasted computing power and confusion. Minor blocks are not very authoritative until they’ve been buried under a major block.

My main motivation for this is as part of an alternate chain distributed betting system, but I haven’t seen it brought up before, and I realize there are probably some good reasons this can’t work. I’m looking forward to comments!