Re: [Bitcoin-development] does stubbing off Merkle trees reduce initial download bandwidth?
It can speed up the initial chain download. A newly created wallet will have only new key-pairs, hence no incoming transactions (unless we have a key collision, which is unlikely). So there is no need for a bootstrapping node to download the chain with transactions. The chain itself can be verified without the transactions. Later full blocks would be required to detect usable inputs for future outgoing transactions. As long as you verify the very last blocks in the chain you can be sure that all preceeding blocks were also valid. HTH, Chris On Mon, Jan 2, 2012 at 6:04 AM, Elden Tyrell tyrell.el...@gmail.com wrote: Satoshi's paper mentions that storage requirements for the blockchain can be reduced by deleting transactions whose outputs have been spent. If I understand correctly, this technique can only be used for reducing *storage* requirements, not *bandwidth* needed for the initial chain download by a high-security client that doesn't trust any of its peers -- right? The rule is trust the longest valid chain of blocks. Part of a block being valid is that each transaction's inputs are unspent and their sum exceeds the transaction's outputs unless it is a coinbase. This cannot be verified for stubbed out transactions -- they have outputs but no inputs, and aren't coinbases. So a paranoid client booting up for the first time needs to be given an un-stubbed chain, right? Of course, if a client decided to accept a stubbed blocks only when the sum of the difficulties in the blocks after it exceeds some number N, then attacking it could be made very expensive by picking a large enough N. Please let me know if I have misunderstood something. -- Ridiculously easy VDI. With Citrix VDI-in-a-Box, you don't need a complex infrastructure or vast IT resources to deliver seamless, secure access to virtual desktops. With this all-in-one solution, easily deploy virtual desktops for less than the cost of PCs and save 60% on VDI infrastructure costs. Try it free! http://p.sf.net/sfu/Citrix-VDIinabox ___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development -- Ridiculously easy VDI. With Citrix VDI-in-a-Box, you don't need a complex infrastructure or vast IT resources to deliver seamless, secure access to virtual desktops. With this all-in-one solution, easily deploy virtual desktops for less than the cost of PCs and save 60% on VDI infrastructure costs. Try it free! http://p.sf.net/sfu/Citrix-VDIinabox___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
Re: [Bitcoin-development] does stubbing off Merkle trees reduce initial download bandwidth?
On Mon, Jan 2, 2012 at 5:23 PM, Elden Tyrell tyrell.el...@gmail.com wrote: On 2012-01-02 05:31:19 -0800, Christian Decker said: Later full blocks would be required to detect usable inputs for future outgoing transactions. Er, yes, this is what I meant; I guess I should have been more specific. So, a paranoid client cannot confirm reciept of coins until it has an unstubbed copy of the entire chain. It can do other things (like send coins) using a stubbed chain, but it needs the whole unstubbed chain in order to be sure that incoming coins haven't already been spent. Thanks for confirming this. Er, no— if a node controls the private keys for a transaction, and that transaction makes it into the chain then it can safely assume that its unspent (at least once its buried a few blocks into the chain). This is the essence of a SPV node. What it can't do is perform this function for txn which aren't its own. Though the system could be extended in a compatible manner to make this possible: https://bitcointalk.org/index.php?topic=21995.0 -- Ridiculously easy VDI. With Citrix VDI-in-a-Box, you don't need a complex infrastructure or vast IT resources to deliver seamless, secure access to virtual desktops. With this all-in-one solution, easily deploy virtual desktops for less than the cost of PCs and save 60% on VDI infrastructure costs. Try it free! http://p.sf.net/sfu/Citrix-VDIinabox ___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
Re: [Bitcoin-development] does stubbing off Merkle trees reduce initial download bandwidth?
On 2012-01-02 14:41:10 -0800, Gregory Maxwell said: make this possible: https://bitcointalk.org/index.php?topic=21995.0 Neat! I had a similar idea but you've clearly beat me to [a big part of] it. Er, no— if a node controls the private keys for a transaction, and that transaction makes it into the chain then it can safely assume that its unspent (at least once its buried a few blocks into the chain). I'm not so sure about that. If you accept X successor blocks as proof that none of the transactions in a block re-used an output, then the cost of attacking is X*50BTC since the hashpower needed for the attack could have earned that much reward. However, an attacker could use the same faked X-block sequence to attack multiple clients by putting several double-spend transactions in the first faked block. This would spread out the cost over more than one attack. So simply checking that the value of the transaction is less than X*50 isn't necessarily enough, although the logistics of the attack aren't exactly easy. There's also the question of knowing what the difficulty for those X blocks ought to be. If the attacker controls your network connection (e.g. your ISP attacks you) you wouldn't be able to get a second opinion on how high the difficulty ought to be, and might get fooled by X very-low-difficulty blocks that were each produced with a lot less than 50BTC worth of hashpower. - e -- Write once. Port to many. Get the SDK and tools to simplify cross-platform app development. Create new or port existing apps to sell to consumers worldwide. Explore the Intel AppUpSM program developer opportunity. appdeveloper.intel.com/join http://p.sf.net/sfu/intel-appdev ___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
[Bitcoin-development] does stubbing off Merkle trees reduce initial download bandwidth?
Satoshi's paper mentions that storage requirements for the blockchain can be reduced by deleting transactions whose outputs have been spent. If I understand correctly, this technique can only be used for reducing *storage* requirements, not *bandwidth* needed for the initial chain download by a high-security client that doesn't trust any of its peers -- right? The rule is trust the longest valid chain of blocks. Part of a block being valid is that each transaction's inputs are unspent and their sum exceeds the transaction's outputs unless it is a coinbase. This cannot be verified for stubbed out transactions -- they have outputs but no inputs, and aren't coinbases. So a paranoid client booting up for the first time needs to be given an un-stubbed chain, right? Of course, if a client decided to accept a stubbed blocks only when the sum of the difficulties in the blocks after it exceeds some number N, then attacking it could be made very expensive by picking a large enough N. Please let me know if I have misunderstood something. -- Ridiculously easy VDI. With Citrix VDI-in-a-Box, you don't need a complex infrastructure or vast IT resources to deliver seamless, secure access to virtual desktops. With this all-in-one solution, easily deploy virtual desktops for less than the cost of PCs and save 60% on VDI infrastructure costs. Try it free! http://p.sf.net/sfu/Citrix-VDIinabox ___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
