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From: Garlo Nicon <garlonicon@gmail.com>
Date: Fri, 26 Sep 2025 09:58:26 +0200
Message-ID: <CAN7kyNgxnKoX7OBLOiHZWLg+9rvisbpmEMrs9RsSMDfeT-sw3w@mail.gmail.com>
Subject: Re: [bitcoindev] [BIP Proposal] Mempool Validation and Relay Policies
 via User-Defined Scripts
To: Andrew Poelstra <apoelstra@wpsoftware.net>
Cc: Bitcoin Development Mailing List <bitcoindev@googlegroups.com>
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> You cannot pick and choose which parts of a block you like and which
parts are "abusive".

In the current implementation, yes. But if you accept a proof, that a block
is valid, instead of accepting a block in plaintext, then you can land on
the same chain. Because after all, pruned nodes care only about the last
288 blocks, or something like that. If they can update their UTXO set, and
always land on a valid chain, then they don't need transaction data in
plaintext. They just need to update their UTXO database in a way, where
attacking it would require breaking ECDSA, SHA-256, or similar things (a
proof-based system, which would not weaken existing cryptographic
assumptions, would be sufficient).

And the same is true about Initial Blockchain Download. Only today, you
have to download hundreds of GBs, to synchronize the new node from scratch.
But it can be changed, and as the size of the whole chain will grow, people
will be pushed, to start deploying some optimizations. Otherwise, there
will be even less nodes, if node operators will decide to trust centralized
solutions instead, or do things, which already happened in some altcoins,
where people passed around an already synced node data, and trusted, that
it is valid (especially in CPU-mined coins, where verifying thousands
blocks required similar effort, than mining a new block).

pt., 26 wrz 2025 o 02:25 Andrew Poelstra <apoelstra@wpsoftware.net>
napisa=C5=82(a):

> On Thu, Sep 25, 2025 at 11:52:02AM -0600, Chris Guida wrote:
> >
> > Anyway, forcing users to relay transactions they consider abusive if th=
ey
> > want to relay any transactions at all does not seem in keeping with
> > bitcoin's ethos, not to mention that it obviously would never work.
> >
>
> Once a transaction is in a block, you need to relay the transaction if
> you want to relay a block. You cannot pick and choose which parts of a
> block you like and which parts are "abusive". This is what it means for
> something to be a consensus system.
>
> The purpose of the mempool is to approximate the contents of blocks,
> both to help individual node operators (who would otherwise get large
> quantities of "surprise transactions" with every block) and to help the
> network (which would otherwise have poor propagation properties).
>
> Any sort of filtering beyond that done by miners is contrary to this
> purpose of the mempool. This is a technical fact. It has nothing to do
> with "bitcoin's ethos", except its ethos as a consensus system, which
> directly contradicts your point.
>
> --
> Andrew Poelstra
> Director, Blockstream Research
> Email: apoelstra at wpsoftware.net
> Web:   https://www.wpsoftware.net/andrew
>
> The sun is always shining in space
>     -Justin Lewis-Webster
>
> --
> You received this message because you are subscribed to the Google Groups
> "Bitcoin Development Mailing List" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to bitcoindev+unsubscribe@googlegroups.com.
> To view this discussion visit
> https://groups.google.com/d/msgid/bitcoindev/aNXRSd7ygh6NqE1V%40mail.wpso=
ftware.net
> .
>

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<div dir=3D"ltr">&gt; You cannot pick and choose which parts of a block you=
 like and which parts are &quot;abusive&quot;.<br><br>In the current implem=
entation, yes. But if you accept a proof, that a block is valid, instead of=
 accepting a block in plaintext, then you can land on the same chain. Becau=
se after all, pruned nodes care only about the last 288 blocks, or somethin=
g like that. If they can update their UTXO set, and always land on a valid =
chain, then they don&#39;t need transaction data in plaintext. They just ne=
ed to update their UTXO database in a way, where attacking it would require=
 breaking ECDSA, SHA-256, or similar things (a proof-based system, which wo=
uld not weaken existing cryptographic assumptions, would be sufficient).<br=
><br>And the same is true about Initial Blockchain Download. Only today, yo=
u have to download hundreds of GBs, to synchronize the new node from scratc=
h. But it can be changed, and as the size of the whole chain will grow, peo=
ple will be pushed, to start deploying some optimizations. Otherwise, there=
 will be even less nodes, if node operators will decide to trust centralize=
d solutions instead, or do things, which already happened in some altcoins,=
 where people passed around an already synced node data, and trusted, that =
it is valid (especially in CPU-mined coins, where verifying thousands block=
s required similar effort, than mining a new block).</div><br><div class=3D=
"gmail_quote gmail_quote_container"><div dir=3D"ltr" class=3D"gmail_attr">p=
t., 26 wrz 2025 o 02:25=C2=A0Andrew Poelstra &lt;<a href=3D"mailto:apoelstr=
a@wpsoftware.net">apoelstra@wpsoftware.net</a>&gt; napisa=C5=82(a):<br></di=
v><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;borde=
r-left:1px solid rgb(204,204,204);padding-left:1ex">On Thu, Sep 25, 2025 at=
 11:52:02AM -0600, Chris Guida wrote:<br>
&gt; <br>
&gt; Anyway, forcing users to relay transactions they consider abusive if t=
hey<br>
&gt; want to relay any transactions at all does not seem in keeping with<br=
>
&gt; bitcoin&#39;s ethos, not to mention that it obviously would never work=
.<br>
&gt;<br>
<br>
Once a transaction is in a block, you need to relay the transaction if<br>
you want to relay a block. You cannot pick and choose which parts of a<br>
block you like and which parts are &quot;abusive&quot;. This is what it mea=
ns for<br>
something to be a consensus system.<br>
<br>
The purpose of the mempool is to approximate the contents of blocks,<br>
both to help individual node operators (who would otherwise get large<br>
quantities of &quot;surprise transactions&quot; with every block) and to he=
lp the<br>
network (which would otherwise have poor propagation properties).<br>
<br>
Any sort of filtering beyond that done by miners is contrary to this<br>
purpose of the mempool. This is a technical fact. It has nothing to do<br>
with &quot;bitcoin&#39;s ethos&quot;, except its ethos as a consensus syste=
m, which<br>
directly contradicts your point.<br>
<br>
-- <br>
Andrew Poelstra<br>
Director, Blockstream Research<br>
Email: apoelstra at <a href=3D"http://wpsoftware.net" rel=3D"noreferrer" ta=
rget=3D"_blank">wpsoftware.net</a><br>
Web:=C2=A0 =C2=A0<a href=3D"https://www.wpsoftware.net/andrew" rel=3D"noref=
errer" target=3D"_blank">https://www.wpsoftware.net/andrew</a><br>
<br>
The sun is always shining in space<br>
=C2=A0 =C2=A0 -Justin Lewis-Webster<br>
<br>
-- <br>
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=3D"_blank">bitcoindev+unsubscribe@googlegroups.com</a>.<br>
To view this discussion visit <a href=3D"https://groups.google.com/d/msgid/=
bitcoindev/aNXRSd7ygh6NqE1V%40mail.wpsoftware.net" rel=3D"noreferrer" targe=
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40mail.wpsoftware.net</a>.<br>
</blockquote></div>

<p></p>

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