(Again nothing new to say here, just putting my notes in this discussion, where I started with an earlier discussion that Peter wrote up with a subject of "disentangling" blockchain design).
In the discussion last year that started the analysis of "disentangling" blockchain design I had broken out the candidate layer properties that one could use as building blocks to construct a decentralised PoW-chain assured immutable history based ecash system as: - time-stamping (really just time-ordered as network time is weak) - namespace (first come first served name value pairs) I thought it was interesting to look at potential minimum enabling functionality in order to explore whether the consensus critical code could be simplified for security, and also to understand the tradeoffs towards seeing if there were any improvements that could be found. (And it seems its pretty hard to find any improvements was my conclusion). Time-stamping (or time-ordering) at a requirements level does not have to imply that there is a uniqueness guarantee, or even that the nodes see what they are time-stamping (it could be committed with a random nonce) and indeed hiding the committed data from the service and public view is a common property of time-stamping. Time-ordering just creates an immutable (and not strongly deduplicated) stream of data items that came from various users and had a time-ordering placed on them. Minimally the person who submitted the data item would need to know the merkle path to it, and that might be achieved by publishing the merkle tree, where some or all of the leaves are hidden commitments. For bitcoin composability purposes you might require that there be no hidden commitments, and then other miners and full nodes could download all the merkle trees for each PoW-interval and ignore duplicates. Namespace service adds the uniqueness and first-come first-served property up-front (as its more efficient for people catching up to not have to download and discard duplicates/double-spends), and this more strict rule requires miners to know about (and presumably index) all previous information to avoid violating this rule. I assume name attributes to hold information like a public key to approve changes in ownership, an IP address, an email address etc. For efficient proof reasons there is still a merkle tree per PoW time-interval binding names into a hash-chain. For bitcoin re-described using a namespace the unique coins are the names, and values and ownership public key etc are attributes of the name; names (coins) are only added (via mining) or after deletion (spend/transfer) of previous names. Transfers are approved via digital signature. The additional property bitcoin requires is that the values add up. I presume the phrase proof of publication means to draw out separately that the full-node version of bitcoin requires a rule that miners should not build on top of blocks unless they have copies of all data committed to. Otherwise a malicious party can hide ownership transfers that can be revealed later, so that no one is assured of ownership: any possibility for a gap in the ownership chain calls into question ownership. So from that perspective a miner consensus rule that it should not build on top of blocks that it hasnt seen a full gap-free history for makes the PoW chain a kind of proof that the miner population at one time saw all data hashed into it. I think you need one more thing which is that the miners (and other full nodes who have copies of the data) are willing to share that historic data with you. There is some meta-incentive for bitcoin holders to help others catchup and be assured of the history and information has to be broadcast as there are many miners and full-nodes. I presume anti-relay term is meant at system level, rather than node level, though technically bitcoin nodes in the current protocol version dont relay double-spent transactions. Particularly that miners wont bless double-spent transactions (and will do PoW only over non double-spent transfers). While there does seem to be some confusion from some people perhaps not realising that it is essential that there are no gaps in the ownership chain, I am not sure there are necessarily any practical implication of philosophical differences between proof of publication & anti-relay (or namespace for that matter). It is also important that there is no way to attack the insertion logic so that eg someone cant get a hash into an internal nor leaf node of the merkle tree without the miners first seeing that data. Presumably as they are all describing ways to think about bitcoin and assuming no one is confused about how bitcoin works, the distinction just comes down to what features are assumed to be naturally included in the layer definition, and what features have to be added. For example I think its relatively normally assumed that people can look up names. I suppose it might be possible to put a self-authenticating access handle for the data item into the data set which points into a redundant immutable data store. In effect that is what the bitcoin nodes do provide (with full redundancy). But, more efficiently though perhaps with less redundancy and assurance, one could put the data into tahoe-lafs which implements immutability, append-only and self-authenticating urls and such properties. From that perspective it does make sense to say there is a layer that provides assurance of availability of history; the PoW-chain and merkle-tree in the header assures already immutability. The remaining thing that has to be assured is availability. Adam On 20 December 2014 at 14:48, Peter Todd <p...@petertodd.org> wrote: > Gregory Maxwell recently pointed out to me in private conservation that > there potentially existed a fundemental disagreement between him and I > on our philosophical approaches to blockchains, in that he prioritised > the notion of the blockchain as an anti-replay oracle, and I prioritised > it as a publication layer. Here I'll talk about the differences and > simularities between those two approaches. ------------------------------------------------------------------------------ Dive into the World of Parallel Programming! The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. 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