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References: <201608232012.12588.luke@dashjr.org>
	<7FF3E128-4D92-46CC-8FBA-9B9E9A9FC7AD@keepkey.com>
From: Gregory Maxwell <greg@xiph.org>
Date: Wed, 24 Aug 2016 08:34:20 +0000
Message-ID: <CAAS2fgSm_5hnP854ygp50FKQnH_5K239b+1E3Zw=ANTU6pe5Sw@mail.gmail.com>
To: Kenneth Heutmaker <ken@keepkey.com>, 
	Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
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Subject: Re: [bitcoin-dev] BIP Status updates (including to Active/Final
 Status) - BIP 39, BIP 43, BIP 44, BIP 67, BIP 111, BIP 125, BIP 130
Precedence: list

On Tue, Aug 23, 2016 at 8:54 PM, Kenneth Heutmaker via bitcoin-dev
<bitcoin-dev@lists.linuxfoundation.org> wrote:
> SPV is kinda broken if the wallet doesn=E2=80=99t do this detection. If y=
our wallet connects only to nodes that don=E2=80=99t support bloom filterin=
g, the wallet never gets updates. We have had a spike in users reporting th=
at their wallet isn't getting updated. To compound the problem, they rescan=
 the blockchain and lose all of their transaction history. It has caused mu=
ch panic among less technical users.
>
> We believe that failing to detect the NODE_BLOOM bit is the culprit, alth=
ough it is non-deterministic, so we aren't certain.

There are almost no NODE_BLOOM supporting bloom-off nodes on the
network currently. So, while supporting this is important, I am
doubtful that its the current problem you've suffered.

There are a great many fake nodes which appear to exist purely to
monitor transactions. Many do not implement enough of the protocol to
support scanning or transaction relay. (and, in fact, relaying
transactions would make monitoring less effective).

You can't count on peers on a peer to peer network to be honest and
cooperative. Implementations need to work hard to be robust to abusive
peers. Unfortunately, the design of the bloom filtering is such that
it isn't always easy (or even possible) to be robust.