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Last Notes

2023-06-07 20:00:17 CEST

- reply

📅 Original date posted:2017-04-17
📝 Original message:1TB HDD is now available for under $40 USD. How is the 100GB storage
requirement preventing anyone from setting up full nodes?
On Apr 16, 2017 11:55 PM, "David Vorick via bitcoin-dev" <
bitcoin-dev at lists.linuxfoundation.org> wrote:
> *Rationale:*
>
> A node that stores the full blockchain (I will use the term archival node)
> requires over 100GB of disk space, which I believe is one of the most
> significant barriers to more people running full nodes. And I believe the
> ecosystem would benefit substantially if more users were running full nodes.
>
> The best alternative today to storing the full blockchain is to run a
> pruned node, which keeps only the UTXO set and throws away already verified
> blocks. The operator of the pruned node is able to enjoy the full security
> benefits of a full node, but is essentially leeching the network, as they
> performed a large download likely without contributing anything back.
>
> This puts more pressure on the archival nodes, as the archival nodes need
> to pick up the slack and help new nodes bootstrap to the network. As the
> pressure on archival nodes grows, fewer people will be able to actually run
> archival nodes, and the situation will degrade. The situation would likely
> become problematic quickly if bitcoin-core were to ship with the defaults
> set to a pruned node.
>
> Even further, the people most likely to care about saving 100GB of disk
> space are also the people least likely to care about some extra bandwidth
> usage. For datacenter nodes, and for nodes doing lots of bandwidth, the
> bandwidth is usually the biggest cost of running the node. For home users
> however, as long as they stay under their bandwidth cap, the bandwidth is
> actually free. Ideally, new nodes would be able to bootstrap from nodes
> that do not have to pay for their bandwidth, instead of needing to rely on
> a decreasing percentage of heavy-duty archival nodes.
>
> I have (perhaps incorrectly) identified disk space consumption as the most
> significant factor in your average user choosing to run a pruned node or a
> lite client instead of a full node. The average user is not typically too
> worried about bandwidth, and is also not typically too worried about
> initial blockchain download time. But the 100GB hit to your disk space can
> be a huge psychological factor, especially if your hard drive only has
> 500GB available in the first place, and 250+ GB is already consumed by
> other files you have.
>
> I believe that improving the disk usage situation would greatly benefit
> decentralization, especially if it could be done without putting pressure
> on archival nodes.
>
> *Small Nodes Proposal:*
>
> I propose an alternative to the pruned node that does not put undue
> pressure on archival nodes, and would be acceptable and non-risky to ship
> as a default in bitcoin-core. For lack of a better name, I'll call this new
> type of node a 'small node'. The intention is that bitcoin-core would
> eventually ship 'small nodes' by default, such that the expected amount of
> disk consumption drops from today's 100+ GB to less than 30 GB.
>
> My alternative proposal has the following properties:
>
> + Full nodes only need to store ~20% of the blockchain
> + With very high probability, a new node will be able to recover the
> entire blockchain by connecting to 6 random small node peers.
> + An attacker that can eliminate a chosen+ 95% of the full nodes running
> today will be unable to prevent new nodes from downloading the full
> blockchain, even if the attacker is also able to eliminate all archival
> nodes. (assuming all nodes today were small nodes instead of archival nodes)
>
> Method:
>
> A small node will pick an index [5, 256). This index is that node's
> permanent index. When storing a block, instead of storing the full block,
> the node will use Reed-Solomon coding to erasure code the block using a
> 5-of-256 scheme. The result will be 256 pieces that are 20% of the size of
> the block each. The node picks the piece that corresponds to its index, and
> stores that instead. (Indexes 0-4 are reserved for archival nodes -
> explained later)
>
> The node is now storing a fragment of every block. Alone, this fragment
> cannot be used to recover any piece of the blockchain. However, when paired
> with any 5 unique fragments (fragments of the same index will not be
> unique), the full block can be recovered.
>
> Nodes can optionally store more than 1 fragment each. At 5 fragments, the
> node becomes a full archival node, and the chosen indexes should be 0-4.
> This is advantageous for the archival node as the encoded data for the
> first 5 indexes will actually be identical to the block itself - there is
> no computational overhead for selecting the first indexes. There is also no
> need to choose random indexes, because the full block can be recovered no
> matter which indexes are chosen.
>
> When connecting to new peers, the indexes of each peer needs to be known.
> Once peers totaling 5 unique indexes are discovered, blockchain download
> can begin. Connecting to just 5 small node peers provides a >95% chance of
> getting 5 uniques, with exponentially improving odds of success as you
> connect to more peers. Connecting to a single archive node guarantees that
> any gaps can be filled.
>
> A good encoder should be able to turn a block into a 5-of-256 piece set in
> under 10 milliseconds using a single core on a standard consumer desktop.
> This should not slow down initial blockchain download substantially, though
> the overhead is more than a rounding error.
>
> *DoS Prevention:*
>
> A malicious node may provide garbage data instead of the actual piece.
> Given just the garbage data and 4 other correct pieces, it is impossible
> (best I know anyway) to tell which piece is the garbage piece.
>
> One option in this case would be to seek out an archival node that could
> verify the correctness of the pieces, and identify the malicious node.
>
> Another option would be to have the small nodes store a cryptographic
> checksum of each piece. Obtaining the cryptographic checksum for all 256
> pieces would incur a nontrivial amount of hashing (post segwit, as much as
> 100MB of extra hashing per block), and would require an additional ~4kb of
> storage per block. The hashing overhead here may be prohibitive.
>
> Another solution would be to find additional pieces and brute-force
> combinations of 5 until a working combination was discovered. Though this
> sounds nasty, it should take less than five seconds of computation to find
> the working combination given 5 correct pieces and 2 incorrect pieces. This
> computation only needs to be performed once to identify the malicious peers.
>
> I also believe that alternative erasure coding schemes exist which
> actually are able to identify the bad pieces given sufficient good pieces,
> however I don't know if they have the same computational performance as the
> best Reed-Solomon coding implementations.
>
> *Deployment:*
>
> Small nodes are completely useless unless the critical mass of 5 pieces
> can be obtained. The first version that supports small node block downloads
> should default everyone to an archival node (meaning indexes 0-4 are used)
>
> Once there are enough small-node-enabled archive nodes, the default can be
> switched so that nodes only have a single index by default. In the first
> few days, when there are only a few small nodes, the previously-deployed
> archival nodes can help fill in the gaps, and the small nodes can be useful
> for blockchain download right away.
>
> ----------------------------------
>
> This represents a non-trivial amount of code, but I believe that the
> result would be a non-trivial increase in the percentage of users running
> full nodes, and a healthier overall network.
>
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev at lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>
>
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2023-06-07 17:36:42 CEST

- reply

📅 Original date posted:2015-06-08
📝 Original message:FWIW, The Open Assets colored coin protocol (CoinPrism) places special
significance on the zeroth input and the position of the OP_RETURN colored
coin marker output to distinguish colored coin issuance outputs from
transfer outputs. Reordering the inputs or the outputs breaks the colored
coin representation.
Recommending sorting of the inputs and outputs as a best practice is fine
(and better than random, IMO), but not as part of IsStandard() or consensus
rules. There are cases where the order of the inputs and outputs is
significant.
-Danny
On Fri, Jun 5, 2015 at 9:42 PM, Rusty Russell <rusty at rustcorp.com.au> wrote:
> Title: Canonical Input and Output Ordering
> Author: Rusty Russell <rusty at rustcorp.com.au>
> Discussions-To: "Bitcoin Dev" <bitcoin-development at lists.sourceforge.net>
> Status: Draft
> Type: Standards Track
> Created: 2015-06-06
>
> Abstract
>
> This BIP provides a canonical ordering of inputs and outputs when
> creating transactions.
>
> Motivation
>
> Most bitcoin wallet implementations randomize the outputs of
> transactions they create to avoid trivial linkage analysis (especially
> change outputs), however implementations have made mistakes in this area
> in the past.
>
> Using a canonical ordering has the same effect, but is simpler, more
> obvious if incorrect, and can eventually be enforced by IsStandard() and
> even a soft-fork to enforce it.
>
> Specification
>
> Inputs should be ordered like so:
> index (lower value first)
> txid (little endian order, lower byte first)
>
> Outputs should be ordered like so:
> amount (lower value first)
> script (starting from first byte, lower byte first, shorter wins)
>
> Rationale
>
> Any single wallet is already free to implement this, but if other
> wallets do not it would reduce privacy by making those transactions
> stand out. Thus a BIP is appropriate, especially if this were to
> become an IsStandard() rule once widely adopted.
>
> Because integers are fast to compare, they're sorted first, before the
> lexographical ordering.
>
> The other input fields do not influence the sort order, as any valid
> transactions cannot have two inputs with the same index and txid.
>
> Reference Implementation
>
> https://github.com/rustyrussell/bitcoin/tree/bip-in-out-ordering
>
>
> ------------------------------------------------------------------------------
> _______________________________________________
> Bitcoin-development mailing list
> Bitcoin-development at lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/bitcoin-development
>
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2023-06-07 17:34:31 CEST

- reply

📅 Original date posted:2015-05-26
📝 Original message:What prevents RBF from being used for fraudulent payment reversals?
Pay 1BTC to Alice for hard goods, then after you receive the goods
broadcast a double spend of that transaction to pay Alice nothing? Your
only cost is the higher network fee of the 2nd tx.
Thanks,
-Danny
On Mon, May 25, 2015 at 5:10 PM, Peter Todd <pete at petertodd.org> wrote:
> On Tue, May 26, 2015 at 12:03:09AM +0200, Mike Hearn wrote:
> > CPFP also solves it just fine.
>
> CPFP is a significantly more expensive way of paying fees than RBF,
> particularly for the use-case of defragmenting outputs, with cost
> savings ranging from 30% to 90%
>
>
> Case 1: CPFP vs. RBF for increasing the fee on a single tx
> ----------------------------------------------------------
>
> Creating an spending a P2PKH output uses 34 bytes of txout, and 148
> bytes of txin, 182 bytes total.
>
> Let's suppose I have a 1 BTC P2PKH output and I want to pay 0.1 BTC to
> Alice. This results in a 1in/2out transaction t1 that's 226 bytes in size.
> I forget to click on the "priority fee" option, so it goes out with the
> minimum fee of 2.26uBTC. Whoops! I use CPFP to spend that output,
> creating a new transaction t2 that's 192 bytes in size. I want to pay
> 1mBTC/KB for a fast confirmation, so I'm now paying 418uBTC of
> transaction fees.
>
> On the other hand, had I use RBF, my wallet would have simply
> rebroadcast t1 with the change address decreased. The rules require you
> to pay 2.26uBTC for the bandwidth consumed broadcasting it, plus the new
> fee level, or 218uBTC of fees in total.
>
> Cost savings: 48%
>
>
> Case 2: Paying multiple recipients in succession
> ------------------------------------------------
>
> Suppose that after I pay Alice, I also decide to pay Bob for his hard
> work demonstrating cryptographic protocols. I need to create a new
> transaction t2 spending t1's change address. Normally t2 would be
> another 226 bytes in size, resulting in 226uBTC additional fees.
>
> With RBF on the other hand I can simply double-spend t1 with a
> transaction paying both Alice and Bob. This new transaction is 260 bytes
> in size. I have to pay 2.6uBTC additional fees to pay for the bandwidth
> consumed broadcasting it, resulting in an additional 36uBTC of fees.
>
> Cost savings: 84%
>
>
> Case 3: Paying multiple recipients from a 2-of-3 multisig wallet
> ----------------------------------------------------------------
>
> The above situation gets even worse with multisig. t1 in the multisig
> case is 367 bytes; t2 another 367 bytes, costing an additional 367uBTC
> in fees. With RBF we rewrite t1 with an additional output, resulting in
> a 399 byte transaction, with just 36uBTC in additional fees.
>
> Cost savings: 90%
>
>
> Case 4: Dust defragmentation
> ----------------------------
>
> My wallet has a two transaction outputs that it wants to combine into
> one for the purpose of UTXO defragmentation. It broadcasts transaction
> t1 with two inputs and one output, size 340 bytes, paying zero fees.
>
> Prior to the transaction confirming I find I need to spend those funds
> for a priority transaction at the 1mBTC/KB fee level. This transaction,
> t2a, has one input and two outputs, 226 bytes in size. However it needs
> to pay fees for both transactions at once, resulting in a combined total
> fee of 556uBTC. If this situation happens frequently, defragmenting
> UTXOs is likely to cost more in additional fees than it saves.
>
> With RBF I'd simply doublespend t1 with a 2-in-2-out transaction 374
> bytes in size, paying 374uBTC. Even better, if one of the two inputs is
> sufficiently large to cover my costs I can doublespend t1 with a
> 1-in-2-out tx just 226 bytes in size, paying 226uBTC.
>
> Cost savings: 32% to 59%, or even infinite if defragmentation w/o RBF
> costs you more than you save
>
> --
> 'peter'[:-1]@petertodd.org
> 0000000000000000134ce6577d4122094479f548b997baf84367eaf0c190bc9f
>
>
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>
>
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