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From: Christian Decker <decker.christian@gmail.com>
Date: Mon, 2 Jan 2012 14:31:19 +0100
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Cc: bitcoin-development@lists.sourceforge.net
Subject: Re: [Bitcoin-development] does "stubbing" off Merkle trees reduce
initial download bandwidth?
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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.elden@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
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--0016e6de16b176bce604b58b9ba2
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Content-Transfer-Encoding: quoted-printable
It can speed up the initial chain download. A newly created wallet will hav=
e 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 usa=
ble 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 a=
lso valid.<br>
<br>HTH,<br>Chris<br><br><div class=3D"gmail_quote">On Mon, Jan 2, 2012 at =
6:04 AM, Elden Tyrell <span dir=3D"ltr"><<a href=3D"mailto:tyrell.elden@=
gmail.com">tyrell.elden@gmail.com</a>></span> wrote:<br><blockquote clas=
s=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;pad=
ding-left:1ex">
Satoshi's paper mentions that storage requirements for the blockchain<b=
r>
can be reduced by deleting transactions whose outputs have been spent.<br>
<br>
If I understand correctly, this technique can only be used for reducing<br>
*storage* requirements, not *bandwidth* needed for the initial chain<br>
download by a high-security client that doesn't trust any of its peers<=
br>
-- right?<br>
<br>
The rule is "trust the longest valid chain of blocks". =A0Part of=
a block<br>
being "valid" is that each transaction's inputs are unspent a=
nd their<br>
sum exceeds the transaction's outputs unless it is a coinbase. =A0This<=
br>
cannot be verified for "stubbed out" transactions -- they have ou=
tputs<br>
but no inputs, and aren't coinbases. =A0So a paranoid client booting up=
<br>
for the first time needs to be given an un-stubbed chain, right?<br>
<br>
Of course, if a client decided to accept a stubbed blocks only when the<br>
sum of the difficulties in the blocks after it exceeds some number N,<br>
then attacking it could be made very expensive by picking a large<br>
enough N.<br>
<br>
Please let me know if I have misunderstood something.<br>
<br>
<br>
<br>
---------------------------------------------------------------------------=
---<br>
Ridiculously easy VDI. With Citrix VDI-in-a-Box, you don't need a compl=
ex<br>
infrastructure or vast IT resources to deliver seamless, secure access to<b=
r>
virtual desktops. With this all-in-one solution, easily deploy virtual<br>
desktops for less than the cost of PCs and save 60% on VDI infrastructure<b=
r>
costs. Try it free! <a href=3D"http://p.sf.net/sfu/Citrix-VDIinabox" target=
=3D"_blank">http://p.sf.net/sfu/Citrix-VDIinabox</a><br>
_______________________________________________<br>
Bitcoin-development mailing list<br>
<a href=3D"mailto:Bitcoin-development@lists.sourceforge.net">Bitcoin-develo=
pment@lists.sourceforge.net</a><br>
<a href=3D"https://lists.sourceforge.net/lists/listinfo/bitcoin-development=
" target=3D"_blank">https://lists.sourceforge.net/lists/listinfo/bitcoin-de=
velopment</a><br>
</blockquote></div><br>
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