From: gabe appleton <gappleto97@gmail•com>
To: Jeff Garzik <jgarzik@bitpay•com>
Cc: Bitcoin Dev <bitcoin-development@lists•sourceforge.net>
Subject: Re: [Bitcoin-development] Proposed additional options for pruned nodes
Date: Tue, 12 May 2015 15:43:45 -0400 [thread overview]
Message-ID: <CANJO25JqoidjKEmi1wv-ACBm6eB-B=g3r5kurLK5O0Gx5orJmA@mail.gmail.com> (raw)
In-Reply-To: <CAJHLa0PDbxuqRHuGNhsyvLpAaDq=ZHSg_u-Sb7FqNVnYrhFkFg@mail.gmail.com>
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Yet this holds true in our current assumptions of the network as well: that
it will become a collection of pruned nodes with a few storage nodes.
A hybrid option makes this better, because it spreads the risk, rather than
concentrating it in full nodes.
On May 12, 2015 3:38 PM, "Jeff Garzik" <jgarzik@bitpay•com> wrote:
> One general problem is that security is weakened when an attacker can DoS
> a small part of the chain by DoS'ing a small number of nodes - yet the
> impact is a network-wide DoS because nobody can complete a sync.
>
>
> On Tue, May 12, 2015 at 12:24 PM, gabe appleton <gappleto97@gmail•com>
> wrote:
>
>> 0, 1, 3, 4, 5, 6 can be solved by looking at chunks chronologically. Ie,
>> give the signed (by sender) hash of the first and last block in your range.
>> This is less data dense than the idea above, but it might work better.
>>
>> That said, this is likely a less secure way to do it. To improve upon
>> that, a node could request a block of random height within that range and
>> verify it, but that violates point 2. And the scheme in itself definitely
>> violates point 7.
>> On May 12, 2015 3:07 PM, "Gregory Maxwell" <gmaxwell@gmail•com> wrote:
>>
>>> It's a little frustrating to see this just repeated without even
>>> paying attention to the desirable characteristics from the prior
>>> discussions.
>>>
>>> Summarizing from memory:
>>>
>>> (0) Block coverage should have locality; historical blocks are
>>> (almost) always needed in contiguous ranges. Having random peers
>>> with totally random blocks would be horrific for performance; as you'd
>>> have to hunt down a working peer and make a connection for each block
>>> with high probability.
>>>
>>> (1) Block storage on nodes with a fraction of the history should not
>>> depend on believing random peers; because listening to peers can
>>> easily create attacks (e.g. someone could break the network; by
>>> convincing nodes to become unbalanced) and not useful-- it's not like
>>> the blockchain is substantially different for anyone; if you're to the
>>> point of needing to know coverage to fill then something is wrong.
>>> Gaps would be handled by archive nodes, so there is no reason to
>>> increase vulnerability by doing anything but behaving uniformly.
>>>
>>> (2) The decision to contact a node should need O(1) communications,
>>> not just because of the delay of chasing around just to find who has
>>> someone; but because that chasing process usually makes the process
>>> _highly_ sybil vulnerable.
>>>
>>> (3) The expression of what blocks a node has should be compact (e.g.
>>> not a dense list of blocks) so it can be rumored efficiently.
>>>
>>> (4) Figuring out what block (ranges) a peer has given should be
>>> computationally efficient.
>>>
>>> (5) The communication about what blocks a node has should be compact.
>>>
>>> (6) The coverage created by the network should be uniform, and should
>>> remain uniform as the blockchain grows; ideally it you shouldn't need
>>> to update your state to know what blocks a peer will store in the
>>> future, assuming that it doesn't change the amount of data its
>>> planning to use. (What Tier Nolan proposes sounds like it fails this
>>> point)
>>>
>>> (7) Growth of the blockchain shouldn't cause much (or any) need to
>>> refetch old blocks.
>>>
>>> I've previously proposed schemes which come close but fail one of the
>>> above.
>>>
>>> (e.g. a scheme based on reservoir sampling that gives uniform
>>> selection of contiguous ranges, communicating only 64 bits of data to
>>> know what blocks a node claims to have, remaining totally uniform as
>>> the chain grows, without any need to refetch -- but needs O(height)
>>> work to figure out what blocks a peer has from the data it
>>> communicated.; or another scheme based on consistent hashes that has
>>> log(height) computation; but sometimes may result in a node needing to
>>> go refetch an old block range it previously didn't store-- creating
>>> re-balancing traffic.)
>>>
>>> So far something that meets all those criteria (and/or whatever ones
>>> I'm not remembering) has not been discovered; but I don't really think
>>> much time has been spent on it. I think its very likely possible.
>>>
>>>
>>> ------------------------------------------------------------------------------
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>>>
>>
>>
>> ------------------------------------------------------------------------------
>> One dashboard for servers and applications across Physical-Virtual-Cloud
>> Widest out-of-the-box monitoring support with 50+ applications
>> Performance metrics, stats and reports that give you Actionable Insights
>> Deep dive visibility with transaction tracing using APM Insight.
>> http://ad.doubleclick.net/ddm/clk/290420510;117567292;y
>> _______________________________________________
>> Bitcoin-development mailing list
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>>
>>
>
>
> --
> Jeff Garzik
> Bitcoin core developer and open source evangelist
> BitPay, Inc. https://bitpay.com/
>
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next prev parent reply other threads:[~2015-05-12 19:43 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CANJO25J1WRHtfQLVXUB2s_sjj39pTPWmixAcXNJ3t-5os8RPmQ@mail.gmail.com>
2015-05-12 15:26 ` gabe appleton
2015-05-12 16:05 ` Jeff Garzik
2015-05-12 16:56 ` gabe appleton
2015-05-12 17:16 ` Peter Todd
2015-05-12 18:23 ` Tier Nolan
2015-05-12 19:03 ` Gregory Maxwell
2015-05-12 19:24 ` gabe appleton
2015-05-12 19:38 ` Jeff Garzik
2015-05-12 19:43 ` gabe appleton [this message]
2015-05-12 21:30 ` [Bitcoin-development] [Bulk] " gb
2015-05-12 20:02 ` [Bitcoin-development] " Gregory Maxwell
2015-05-12 20:10 ` Jeff Garzik
2015-05-12 20:41 ` gabe appleton
2015-05-12 20:47 ` Gregory Maxwell
[not found] ` <CAFVoEQTdmCSRAy3u26q5oHdfvFEytZDBfQb_fs_qttK15fiRmg@mail.gmail.com>
[not found] ` <CAJHLa0OxxxiVd3JOp8SDvbF8dHj6KHdUNGb9L_GvTe93z3Z8mg@mail.gmail.com>
[not found] ` <CAJHLa0MYSpVBD4VE65LVbADb2daOvE=N83G8F_zDSHy3AQ5DAQ@mail.gmail.com>
2015-05-12 21:17 ` [Bitcoin-development] Fwd: " Adam Weiss
2015-05-12 22:00 ` [Bitcoin-development] " Tier Nolan
2015-05-12 22:09 ` gabe appleton
2015-05-13 5:19 ` Daniel Kraft
2015-05-13 9:34 ` Tier Nolan
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