Topic: Proposal: A Second Chain for Scalability (Read 3976 times)

I like the idea about merged-mined second chain since its optional and non-disruptive.
I think you should go for it etotheipi!
It will be your answer to a competing Electrum/Startum client-server approach.
You have a large group of followers with Armory, so adoption shouldn't be a problem.

At some point in time Armory would need to get rid of bitcoind dependency for networking.
That would be the right time to introduce the concept!

PS: I recently started using Armory for off-line transactions and I love it

I don't think that I'm expressing myself well here.  I not 'scoffing' at the idea that some clients need live Interent access in order to function.  I'm saying that more than one method to support lightweight clients that require live Internet already exist, and none of them actually require the resource overhead of an alt-chain.  Make no mistake, the distributed security of bitcoin is an awesome thing, but it's also expensive in many ways.  Murged mining helps in that regard to a limited degree, but it's a crude kind of hack.  Not at all the smooth, elegant & interwoven solution that bitcoin itself is.

What I want is a lightweight client, that can run on my Android phone, and if the cell network is down (snowstorm, Katrina, zombie outbreak, whatever) or I'm deliberately out of my service zone (camping, safari, fishing trip, whatever) my light android client can still transact to some degree sans live Internet.  The light client as described in Satoshi's white paper, that holds the block headers & copies of it's own input transactions; can spend bitcoins because it can create & sign a proper transaction.  It can also receive a transaction.  What it can't do, without live Internet, is check the validity of a transaction; beyond checking to see if the provided input transactions fit into the Merkle tree.  Even with live Interent, an independent light client can't do that nor discover new transactions for itself without scanning whole blocks itself.  That's teh role that both Stratum & this proposal seem to fill.  If this proposal requires live internet at the time of transaction,then it offers no practical advantages over Stratum.  Stratum is, itself, a distributed p2p netowrk protocol.  It may not look like bitcoin, but it doesn't need to either.


No, not must.  A client with the block headers, copies of the transactions used to send money to it's own addresses (it's input transactions) and a local wallet.dat can create & sign transctions locally, and it can thus use any of a number of ways to communicate that transction over to the vendor; who then may or may not be able to verify it and may or may not be able to forward that transaction to the Internet immediately.  These are not requirements.  However, a client that holds only a wallet.dat would need the live support of a Stratum server to construct it's own transaction, so that kind of (ultralight?) client would require live internet.


It's not slightly more to download.  It's at least as much with potentially several orders of magnitude more to download, store & verify.  There is also the multiplicity issue with blockchains.  Bitcoin requires that multiplicity of redundent data, but the light clients do not.  That is one of the driving forces for overlay networks such as Stratum, to limit the multiplicity.  just because you might not be seeing that across your own data plan, doesn't mean that someone doesn't need to pay for that extra duplication of effort as well.  One way or another, the end users are going to be paying for the network. 

I can see that, what I can't see is what gain is there in downloading a regualr digest of a pruned blockchain, when you could just help finish the touches on pruning and do the exact same thing within the bitcoin netowrk, no murged mining hack nor additional network resources required.  What you guys  are trying to acomplish is already possible within the protocol.  Without additional advantages, why bother?

And this is another thing, that is one huge assumption.  We didn't know that bitcoin itself would work two years ago.  How do you know that murged mining works as described?  I sure don't.


While dicks will always be dicks, those dicks can't really steal anything of significance, and the high costs of doing what you are talking about is a huge deterrent.

That may be a fairly strong positive to some while at the same time a significant negative to others.  This is a hypothesis which seems to me to explain the somewhat amusing failures between different individuals to conceptualize one another's views on possible future trajectories of Bitcoin and beyond that, crypto-accounting solutions generally.

Okay, we're comparing to the same thing, at least.  The Stratum servers can be set to communicate with a full-node that you trust, but many users will either pay a fee to use one, or trust based on majority response from a bunch of free servers.  When the latter is used, you can get awfully creative in trying to figure out what servers are telling you the truth, profiling them, blacklisting nodes, etc. 

What I don't get is why you scoffed at the necessity of having a connection, but I don't know how the Stratum overlay network you describe can work without a connection...?   You must contact one of the servers in order to construct your outgoing transaction, right?  So why not connect to a alt-chain node and query your address balances the same way?  It's slightly more data to download, but it requires zero setup, zero trust, and uses the same networking protocols already used everywhere else (because it's already done in Bitcoin-Qt and the variants used for merged mining nodes). 

Again, you can download your entire unspent-TxOut-list from any node with the same confidence as a full node.  If you don't see it, then you didn't understand the proposal.  This is assuming that the second chain is secure, but I'm pretty sure merged mining is taking care of that.

As for the spoofing -- people don't need a good a reason to be dicks, they may just want to disrupt stuff.  For a "small price" they may be able to disrupt an otherwise useful network, enough that people stop even bothering using it, and accept lower-confidence data.  Or just stop using Bitcoin.  There doesn't need to be a good reason for it, because anything is a good reason to the person actually doing it. 

Stratum uses a different model.  I'm not one of the developers, so I only understand what the intent is; but each stratum server is a full bitcoin client first, and also participates in the secondary network.  The stratum servers don't depend upon each other to do anything outside of what the bitcoin network already does.  The stratum protocol functions as a controlled spigot to the bitcoin network firehose.  A stratum capable client can query a single stratum server that the user trusts (because he has a service paid for, or because he personally set up that particular server) and privately query the stratum server for data about particular addresses or transactions.  The client, should it not trust any particular server, can reach out to several stratum servers in a semi-random way (either biased towards servers that it has contacted before and not be told falsehoods, or by some other method) and query multiple servers and check responses against each other.  It provides a standard method for a single full bitcoin node to function as the blockchain to hundreds or thousands of light clients, that may or may not actually maintain either block headers or transaction inputs.  Like a distributed version of a split wallet service, like BitcoinSpinner without the vendor lock-in.


That a remote possibility, but again most of the light clients that we expect to see in the future will be desktop apps that don't mine but are still capable of switching to full node mode at will or by user direction.  If the stratum network is being DDOSed, or is otherwise unreachable, most (probably not all) such clients would simply jump directly onto the main bitcoin network to acheive their ends.  This is likely to cause problems in it's own right, but the option always remains open.


I'm skeptical of that, myself.  I will reserver my final judgement based upon what you can show me later.


First, it can compare to local blockheaders, it's just not limited to that.

Second, see above about checking several servers against each other, or simply running your own stratum server at home for use on your android.


You make that sound like that's easy to do, or cheap.  Yes, such an attack vector is possible under thin conditions.  Still, it's potential gain is limited to what the spoofed client is willing to send or what he believes that he has received, not all he has.  I can't see all that kind of effort just to steal my lunch money.  If you're buying a new car with bitcoin, you're going to be taking some more deliberate steps anyway.  The general trend is that security & convience are at odds to each other, and these light clients are intended for convience with relative security, not the full absolute security that a hardened full client could provide while also running it on a cell phone.  This also doesn't consider the use of risk assessment algos.  For example, if your client tries to reach out to the stratum network to check a transaction sent to itself, but can't connect to your personal stratum server, so it falls back to polling 8 random servers & eight servers from within it's own 'good' history.  It gets back all the right responses, but the version number of the nodes it knew about all have different checksums than last time.  Could be that you haven't used this app in a while and everyone really has upgraded, or it could be that you've been corralled into a honey-pot network.  The client notifies you of it's risk assesment, you can either take the transaction on faith or reject it and refuse to hand over the product.


True.  You also need the same from an alt-chain just to be able to have one.  That only shifts the problem across time, it does not change teh problem logically.


Once the block has been created, true.  Not true while the block is being settled upon.  This is why bitcoin, itslef, requires 6 confirmations before the standar client will resend the coins.


My understanding of merged mining is limited, but my understanding of regular proof-of-work is not.  That said, as I undertstand it, merged mining permits the alt chain to leverage bitcoin's securlty to shore up it's own; generally by inerweaving specially identified transactions into the bitcoin blocks, while interweaving all or part of the last bitcoin block's header into the alt-chains's header; thus proving a time sequence in lockstep with bitcoin's own.  While this little hack would permit a mnor alt-chain to benefit from the securty of the bitcoin blockchain, it does nothing that I know of to actually improve teh trustworthyness of the miners that created the alt-chain block to begin with.  Does namecoin do this?

  You're right,  I was confused.  Thanks.

Sorry, I'm not familiar with the Stratum alternative.  If there is no alt-chain for verification, what is stopping malicious nodes from distributing bogus data to the rest of the network?  Someone malicious can effectively DoS a significant proportion of lite nodes just by setting up a thousands of fake peers that connect to as many other peers as possible and all give out the same incorrect data.  It might take more work for nodes to sort it out than if you just decided to be a full node (credit to Casascius for this argument).

This goes back to the original source of this thread:  an overlay network makes sense in some contexts, but perhaps using an alt-chain secured through merged mining might be a better alternative (albeit more complex).

Under what criteria does a node decide that important data is correct in an overlay network if there is no way to compare directly to the blockheaders?   It seems that to do this in a decentralized manner without an alt-chain,  you have to trust whatever information is given to you by the majority of your peers.  But peers are cheap and easily spoofed.  One resourceful attacker can muck up the entire network with a million fake nodes.  This is where an alt-chain is beneficial:

--In a non-alt-chain network, you need a majority of nodes telling you the correct answer to end up with the correct answer
--With an alt-chain secured through merged mining, it only takes only one honest node for you to get the correct answer (verified through proof-of-work), even if the other 999 peers are malicious

Unfortunately, my understanding of merged mining and Stratum's overlay network is really weak.  Please fill me in if I'm missing the mark.

Probably, under certain conditions. 

Couldn't merged mining be used to secure the alt-chain?

Then this proposal is already a fail.  Because what do you offer then?  Decentralization?  You might as well say 'the cloud' for all the relevance that would have to the end user.