Thanks for giving serious consideration to my post. With regard to your question "if a transaction spends a "coin" that ends in "1" and creates a new coin that ends in "1", which partition should process the transaction?", I would answer that only one partition is involved. In other words, there are N independent block chains that never cross paths.
With regard to your question "what is the prior data needed to validate that kind of TXs?" I do not understand what this means. If you can dumb it down a bit that would be good because there could be some interesting concern in this question. Since partitions are completely segregated, there is no need for a node to work on multiple partitions simultaneously. For attacks to be defeated a node needs to be able to work on multiple partitions in turn, not at the same time. The reason is because if the computing power of the good-faith nodes is unbalanced this gives attackers an unfair advantage. On 12/9/15, Loi Luu via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org> wrote: > Dear Akiva, > > Its Loi Luu, one of the authors of the SCP protocol ( > http://eprint.iacr.org/2015/1168.pdf ). > > Before SCP, we had been thinking hard about how to do sharding efficiently > without degrading any security guarantee. A simple solution which splits > the coins, or TXs in to several partitions will just not work. You have to > answer more questions to have a good solutions. For example, I wonder in > your proposal, if a transaction spends a "coin" that ends in "1" and > creates a new coin that ends in "1", which partition should process the > transaction? What is the prior data needed to validate that kind of TXs? > > The problem with other proposals, and probably yours as well, that we see > is that the amount of data that you need to broadcast immediately to the > network increases linearly with the number of TXs that the network can > process. Thus, sharding does not bring any advantage than simply using > other techniques to publish more blocks in one epoch (like Bitcoin-NG, > Ghost). The whole point of using sharding/ partition is to localize > the bandwidth used, and only broadcast only a minimal data to the network. > > Clearly we are able to localize the bandwidth used with our SCP protocol. > The cost is that now recipients need to themselves verify whether a > transaction is double spending. However, we think that it is a reasonable > tradeoff, given the potential scalability that SCP can provides. > > Thanks, > Loi Luu. > > On Wed, Dec 9, 2015 at 12:27 AM, Akiva Lichtner via bitcoin-dev < > bitcoin-dev@lists.linuxfoundation.org> wrote: > >> Hello, >> >> I am seeking some expert feedback on an idea for scaling Bitcoin. As a >> brief introduction: I work in the payment industry and I have twenty >> years' >> experience in development. I have some experience with process groups and >> ordering protocols too. I think I understand Satoshi's paper but I admit >> I >> have not read the source code. >> >> The idea is to run more than one simultaneous chain, each chain defeating >> double spending on only part of the coin. The coin would be partitioned >> by >> radix (or modulus, not sure what to call it.) For example in order to >> multiply throughput by a factor of ten you could run ten parallel chains, >> one would work on coin that ends in "0", one on coin that ends in "1", >> and >> so on up to "9". >> >> The number of chains could increase automatically over time based on the >> moving average of transaction volume. >> >> Blocks would have to contain the number of the partition they belong to, >> and miners would have to round-robin through partitions so that an >> attacker >> would not have an unfair advantage working on just one partition. >> >> I don't think there is much impact to miners, but clients would have to >> send more than one message in order to spend money. Client messages will >> need to enumerate coin using some sort of compression, to save space. >> This >> seems okay to me since often in computing client software does have to >> break things up in equal parts (e.g. memory pages, file system blocks,) >> and >> the client software could hide the details. >> >> Best wishes for continued success to the project. >> >> Regards, >> Akiva >> >> P.S. I found a funny anagram for SATOSHI NAKAMOTO: "NSA IS OOOK AT MATH" >> >> >> _______________________________________________ >> bitcoin-dev mailing list >> bitcoin-dev@lists.linuxfoundation.org >> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev >> >> > _______________________________________________ bitcoin-dev mailing list bitcoin-dev@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
