Re: [bitcoin-dev] Solving the Scalability Problem on Bitcoin

[Leandro Coutinho via bitcoin-dev]

>>> 5) The problem with node pruning is that it is not standardized, and
for a new node to enter the network and to verify the data, it needs to
download all data and prune it by itself. This will drastically lower the
information needed by the full nodes by getting rid of the junk.  Currently
we are around 140GB, that number is getting bigger exponentially, by the
number of users and transactions created. It could reach a Terrabyte sooner
than expected, we need to act now.

To have to download all blockchain for then prune is a big drawback.
So I thought about the concept of "trusted" nodes, where you could choose
some nodes to connect and from which block you want to download. Of course
they would do this by their own risk, but there are ways to minimize the
risk, like:
  - check the latest blocks (hashes) if they match what you find in some
sites, like blockchain.info
  - download and compare the utxo from all (some) the nodes you are
connected

Currently utxo size is around 2GB and we cant know how fast it will grow (?)

Em 26/08/2017 19:39, "Adam Tamir Shem-Tov via bitcoin-dev" <
bitcoin-dev@lists.linuxfoundation.org> escreveu:

Thank you Thomas for your response.

1) Implement solution is impossible... I have given a solution in part II.
By adding a Genesis Account which will be the new sender.

2)Keeping older blocks: Yes as I said 10 older blocks should be kept, that
should suffice. I am not locked on that number, if you think there is a
reason to keep more than that, it is open to debate.

3) Why 1000? To be honest, that number came off the top of my head. These
are minor details, the concept must first be accepted, then we can work on
the minor details.

4)Finally it's not just the addresses and balance you need to save...  I
think the Idea of the Genesis Account, solves this issue.

5) The problem with node pruning is that it is not standardized, and for a
new node to enter the network and to verify the data, it needs to download
all data and prune it by itself. This will drastically lower the
information needed by the full nodes by getting rid of the junk.  Currently
we are around 140GB, that number is getting bigger exponentially, by the
number of users and transactions created. It could reach a Terrabyte sooner
than expected, we need to act now.

On your second email:
When I say account: I mean private-public key.
The way bitcoin works, as I understand it, is that the funds are verified
by showing that they have an origin, this "origin" needs to provide a
signature, otherwise the transaction won't be accepted.
If I am proposing to remove all intermediate origins, then the funds become
untraceable and hence unverifiable. To fix that, a new transaction needs to
replace old ones. A simplified version: If there was a transaction chain
A->B->C->D, and I wish to show only A->D, only a transaction like that
never actually occurred, it would be impossible to say that it did without
having A's private key, in order to sign this transaction. In order to
create this transaction, I need A's private key. And if I wish this to be
publicly implemented I need this key to be public, so that any node
creating this Exodus Block can sign with it. Hence the Genesis Account. And
yes, it is not really an account.

On 27 August 2017 at 00:31, Thomas Guyot-Sionnest  wrote:

> Pruning is already implemented in the nodes... Once enabled only unspent
> inputs and most recent blocks are kept. IIRC there was also a proposal to
> include UTXO in some blocks for SPV clients to use, but that would be
> additional to the blockchain data.
>
> Implementing your solution is impossible because there is no way to
> determine authenticity of the blockchain mid way. The proof that a block
> hash leads to the genesis block is also a proof of all the work that's been
> spent on it (the years of hashing). At the very least we'd have to keep all
> blocks until a hard-coded checkpoint in the code, which also means that as
> nodes upgrades and prune more blocks older nodes will have difficulty
> syncing the blockchain.
>
> Finally it's not just the addresses and balance you need to save, but also
> each unspent output block number, tx position and script that are required
> for validation on input. That's a lot of data that you're suggesting to
> save every 1000 blocks (and why 1000?), and as said earlier it doesn't even
> guarantee you can drop older blocks. I'm not even going into the details of
> making it work (hard fork, large block sync/verification issues, possible
> attack vectors opened by this...)
>
> What is wrong with the current implementation of node pruning that you are
> trying to solve?
>
> --
> Thomas
>
> On 26/08/17 03:21 PM, Adam Tamir Shem-Tov via bitcoin-dev wrote:
>
>  Solving the Scalability issue for bitcoin  
>
> I have this idea to solve the scalability problem I wish to make public.
>
> If I am wrong I hope to be corrected, and if I am right we will all gain
> by it. 
>
> Currently each block 

Re: [bitcoin-dev] Small Nodes: A Better Alternative to Pruned Nodes

[Leandro Coutinho via bitcoin-dev]

Maybe it already exists ...

#9484  812714f
 Introduce assumevalid
setting to skip validation presumed valid scripts (gmaxwell)
https://github.com/bitcoin/bitcoin/pull/9484

..., but ...
It would be very interesting if a new node could decide to be a pruned node:
  - it would need to trust one or more peers for the initial blockchain
download, because the blocks downloaded would not be validated
  - it would decide a time from when to get the blocks, like a week before
  - once a day a routine would run that would prune blocks older than the
chosen time

"

*The unspent transaction outputs (which is the only essential piece ofdata
necessary for validation) are already kept in a separate database,so
technically removing old blocks is perfectly possible.*" Pieter Wuille
https://bitcoin.stackexchange.com/questions/11170/why-is-pruning-not-considered-already-at-the-moment


On Fri, Apr 21, 2017 at 10:35 AM, David Kaufman via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> Hi Danny,
>
> On Mon, Apr 17, 2017 at 3:11 AM, Danny Thorpe wrote:
> >
> > 1TB HDD is now available for under $40 USD.  How is the 100GB storage
> > requirement preventing anyone from setting up full nodes?
>
> Yeah, but that's because most people (well, using myself as the
> "target market" anyway) are upgrading to SSD's for the faster boot and
> response times.  Modern consumer OS's run incredibly slow on
> non-ssd drives!  And since the vast majority of consumer laptops sold
> today fall into the $400 to $700 range, a 200 - 500gb SSD is about the
> most storage upgrade people can afford.
>
> And so I think David's premise, that having to devote only 30GB to
> running a full node instead of 100, would remove a major obstacle that
> prevents many more people running full bitcoin nodes.
>
> My only suggestion is, does it scale?  I mean, if the bitcoin network
> volume grows exponentially and in 2 years the blockchain is 500GB, can
> the "small node" be adjusted down from one fifth of the blockchain to
> just one-tenth, or one twentieth?  Can different smalInesses
> interoperate? Can I choose to store a small node with 20 - 30% of the
> blockchain, while others chose to share just 5% or 10% of it? Can I run
> "less small" node today that's 50GB?
>
> Can the default install be a "small node" that requires about 30GB of
> storage (if that is indeed the sweet spot for enticing many more users to
> bringing nodes online), but allow the user at install time, to choose *how*
> small? To, say, drag a slider anywhere up and down the range from
> 10GB to 100GB?
>
> If not, then it will have to be revisited constantly as the blockchain
> grows, and disk storage prices drop.  I suspect the blockchain will
> grow in size, at some point in the not too distant future, much faster
> than storage prices drop, so making small, smaller and smallest nodes
> that can be configured to store more or less of it will be necessary
> to motivate most users to run nodes at all.  But when that happens,
> there is likely to be exponentially *more* people using bitcoin, too!
> So an exponentially growing number of users running (smaller and
> smaller) nodes would take up the slack.
>
> Then, the blockchain would begin to look a lot more like a bittorrent,
> right? ;-) but -- happily -- one that you never need to download fully.
>
> -dave
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Re: [bitcoin-dev] Hard fork proposal from last week's meeting

[Leandro Coutinho via bitcoin-dev]

One interesting thing to do is to compare how much does it cost to maintain
a bank check account and how much does it cost to run a full node.

It seems that it is about 120USD/year in USA:
http://m.huffpost.com/us/entry/6219730

A 4TB hard drive ~=115USD
https://www.amazon.com/gp/aw/d/B01LQQH86A/ref=mp_s_a_1_4

And it has a warranty of 3 years.

As your calculation shows, it will take more than 19 years to reach 4TB
with a 4MB blocksize.

Em 29/03/2017 12:35, "Johnson Lau via bitcoin-dev" <
bitcoin-dev@lists.linuxfoundation.org> escreveu:


On 29 Mar 2017, at 14:24, Emin Gün Sirer via bitcoin-dev  wrote:

>Even when several of the experts involved in the document you refer has my
respect and admiration, I do not agree with some of their conclusions

I'm one of the co-authors of that study. I'd be the first to agree with
your conclusion
and argue that the 4MB size suggested in that paper should not be used
without
compensation for two important changes to the network.


Our recent measurements of the Bitcoin P2P network show that network speeds
have improved tremendously. From February 2016 to February 2017, the average
provisioned bandwidth of a reachable Bitcoin node went up by approximately
70%.
And that's just in the last year.


4 * 144 * 30 = 17.3GB per month, or 207GB per year. Full node
initialisation will become prohibitive for most users until a shortcut is
made (e.g. witness pruning and UTXO commitment but these are not trust-free)


Further, the emergence of high-speed block relay networks, like Falcon (
http://www.falcon-net.org)
and FIBRE, as well as block compression, e.g. BIP152 and xthin, change the
picture dramatically.


Also as the co-author of the selfish mining paper, you should know all
these technology assume big miners being benevolent.


So, the 4MB limit mentioned in our paper should not be used as a protocol
limit today.

Best,
- egs



On Tue, Mar 28, 2017 at 3:36 PM, Juan Garavaglia via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> Alphonse,
>
>
>
> Even when several of the experts involved in the document you refer has my
> respect and admiration, I do not agree with some of their conclusions some
> of their estimations are not accurate other changed like Bootstrap Time,
> Cost per Confirmed Transaction they consider a network of 450,000,00 GH and
> today is 3.594.236.966 GH, the energy consumption per GH is old, the cost
> of electricity is wrong even when the document was made and is hard to find
> any parameter used that is valid for an analysis today.
>
>
>
> Again with all respect to the experts involved in that analysis is not
> valid today.
>
>
>
> I tend to believe more in Moore’s law, Butters' Law of Photonics and
> Kryder’s Law all has been verified for many years and support that 32 MB in
> 2020 are possible and equals or less than 1 MB in 2010.
>
>
>
> Again may be is not possible Johnson Lau and LukeJr invested a significant
> amount of time investigating ways to do a safe HF, and may be not possible
> to do a safe HF today but from processing power, bandwidth and storage is
> totally valid and Wang Chung proposal has solid grounds.
>
>
>
> Regards
>
>
>
> Juan
>
>
>
>
>
> *From:* Alphonse Pace [mailto:alp.bitc...@gmail.com]
> *Sent:* Tuesday, March 28, 2017 2:53 PM
> *To:* Juan Garavaglia ; Wang Chun <1240...@gmail.com>
> *Cc:* Bitcoin Protocol Discussion 
>
> *Subject:* Re: [bitcoin-dev] Hard fork proposal from last week's meeting
>
>
>
> Juan,
>
>
>
> I suggest you take a look at this paper: http://fc16.ifca.ai/bit
> coin/papers/CDE+16.pdf  It may help you form opinions based in science
> rather than what appears to be nothing more than a hunch.  It shows that
> even 4MB is unsafe.  SegWit provides up to this limit.
>
>
>
> 8MB is most definitely not safe today.
>
>
>
> Whether it is unsafe or impossible is the topic, since Wang Chun proposed
> making the block size limit 32MiB.
>
>
>
>
>
> Wang Chun,
>
>
> Can you specify what meeting you are talking about?  You seem to have not
> replied on that point.  Who were the participants and what was the purpose
> of this meeting?
>
>
>
> -Alphonse
>
>
>
> On Tue, Mar 28, 2017 at 12:33 PM, Juan Garavaglia  wrote:
>
> Alphonse,
>
>
>
> In my opinion if 1MB limit was ok in 2010, 8MB limit is ok on 2016 and
> 32MB limit valid in next halving, from network, storage and CPU perspective
> or 1MB was too high in 2010 what is possible or 1MB is to low today.
>
>
>
> If is unsafe or impossible to raise the blocksize is a different topic.
>
>
>
> Regards
>
>
>
> Juan
>
>
>
>
>
> *From:* bitcoin-dev-boun...@lists.linuxfoundation.org [mailto:
> bitcoin-dev-boun...@lists.linuxfoundation.org] *On Behalf Of *Alphonse
> Pace via bitcoin-dev
> *Sent:* Tuesday, March 28, 2017 2:24 PM
> *To:* Wang Chun <1240...@gmail.com>; Bitcoin Protocol Discussion <
> bitcoin-dev@lists.linuxfoundation.org>
> *Subject:* 

Re: [bitcoin-dev] SHA1 collisions make Git vulnerable to attakcs by third-parties, not just repo maintainers

[Leandro Coutinho via bitcoin-dev]

If people split their bitcoins in multiple addresses, then maybe there
would be no need to worry(?), because the computational cost would be
higher than what the attacker would get.


>From Google:
https://security.googleblog.com/2017/02/announcing-first-sha1-collision.html

*Here are some numbers that give a sense of how large scale this
computation was: *

   - *Nine quintillion (9,223,372,036,854,775,808) SHA1 computations in
   total*
   - *6,500 years of CPU computation to complete the attack first phase*
   - *110 years of GPU computation to complete the second phase*


https://bitinfocharts.com/top-100-richest-bitcoin-addresses.html
Richest address: 124,178 BTC ($142,853,079 USD)



On Sat, Feb 25, 2017 at 6:40 PM, Peter Todd via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> On Sat, Feb 25, 2017 at 03:34:33PM -0600, Steve Davis wrote:
> > Yea, well. I don’t think it is ethical to post instructions without an
> associated remediation (BIP) if you don’t see the potential attack.
>
> I can't agree with you at all there: we're still at the point where the
> computational costs of such attacks limit their real-world impact, which is
> exactly when you want the *maximum* exposure to what they are and what the
> risks are, so that people develop mitigations.
>
> Keeping details secret tends to keep the attacks out of public view, which
> might be a good trade-off in a situation where the attacks are immediately
> practical and the need to deploy a fix is well understood. But we're in the
> exact opposite situation.
>
> > I was rather hoping that we could have a fuller discussion of what the
> best practical response would be to such an issue?
>
> Deploying segwit's 256-bit digests is a response that's already fully
> coded and
> ready to deploy, with the one exception of a new address format. That
> address
> format is being actively worked on, and could be deployed relatively
> quickly if
> needed.
>
> --
> https://petertodd.org 'peter'[:-1]@petertodd.org
>
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Re: [bitcoin-dev] SHA1 collisions make Git vulnerable to attakcs by third-parties, not just repo maintainers

[Leandro Coutinho via bitcoin-dev]

Google recommeds "migrate to safer cryptographic hashes such as SHA-256 and
SHA-3"
It does not mention RIPEMD-160

https://security.googleblog.com/2017/02/announcing-first-sha1-collision.html?m=1


Em 25/02/2017 10:47, "Steve Davis via bitcoin-dev" <
bitcoin-dev@lists.linuxfoundation.org> escreveu:


> On Feb 24, 2017, at 7:01 PM, Peter Todd  wrote:
>
> On Fri, Feb 24, 2017 at 05:49:36PM -0600, Steve Davis via bitcoin-dev
wrote:
>> If the 20 byte SHA1 is now considered insecure (with good reason), what
about RIPEMD-160 which is the foundation of Bitcoin addresses?
>
> SHA1 is insecure because the SHA1 algorithm is insecure, not because
160bits isn't enough.
>
> AFAIK there aren't any known weaknesses in RIPEMD160,

…so far. I wonder how long that vacation will last?

> but it also hasn't been
> as closely studied as more common hash algorithms.

...but we can be sure that it will be, since the dollar value held in
existing utxos continues to increase...

> That said, Bitcoin uses
> RIPEMD160(SHA256(msg)), which may make creating collisions harder if an
attack
> is found than if it used RIPEMD160 alone.

Does that offer any greater protection? That’s not so clear to me as the
outputs (at least for p2pkh) only verify the public key against the final
20 byte hash. Specifically, in the first (notional) case the challenge
would be to find a private key that has a public key that hashes to the
final hash. In the second (realistic) case, you merely need to add the
sha256 hash into the problem, which doesn’t seem to me to increase the
difficulty by any significant amount?


/s
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