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From: Leo Wandersleb <leo@LeoWandersleb.de>
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Date: Wed, 4 Jan 2017 17:13:41 +0100
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Subject: Re: [bitcoin-dev] Committed bloom filters for improved wallet
 performance and SPV security
Precedence: list

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On 01/04/2017 12:06 AM, adiabat via bitcoin-dev wrote:
> Also, if you're running a light client, and storing the filters the way=
 you
> store block headers, there's really no reason to go all the way back to=
 height
> 0.  You can start grabbing headers at some point a while ago, before yo=
ur set
> of keys was generated.  I think it'd be very worth it even with GB-scal=
e disk
> usage.

The really great benefit of having this index is that you could implement=
 rather
efficient cold wallet spending once the wallet has the full index.

With Mycelium you can currently spend funds from a paper wallet or a BIP3=
9
sentence but at the cost of sharing all addresses with our servers. Schil=
dbach
would share addresses with random full nodes for hours or days to find fu=
nds of
a new private key with unknown creation date. With CBF it would still be =
a
matter of maybe minutes on a phone to identify relevant blocks and downlo=
ad
these but it would be very feasible to implement a private, cold storage
spending feature.

Also the index could be further partitioned by P2PKH, P2PK, P2SH, =85 Thi=
s would
lead to a very minor privacy leak for a reasonable reduction in index siz=
e.

--=20

Leo Wandersleb


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