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From: Peter Todd <pete@petertodd.org>
Date: Wed, 09 Apr 2014 14:04:46 -0400
To: Tamas Blummer <tamas@bitsofproof.com>
Message-ID: <1fa234ec-9dd4-45de-8ac8-ca20a158c344@email.android.com>
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Cc: bitcoin-development@lists.sourceforge.net
Subject: Re: [Bitcoin-development] Bitcoind-in-background mode for
	SPV	wallets
Precedence: list

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On 9 April 2014 13:50:03 GMT-04:00, Tamas Blummer <tamas@bitsofproof.com>=
 wrote:
>Block header has to be available in SPV and also in an UTXO only
>storing core node, so why not serve it if bandwith allows.
>
>Serving any additional information like known peer adresses or known
>full blocks is certainly beneficial and should be offered if at hand.

Big security advantages too. For instance if an attacker hacks, say, 10=E2=
=84=85 of hashing power the next step for them to attack SPV clients is t=
o try to Sybil attack them so they won't find out about the longer chain.=
 The fewer providers of block chain data there are out there the easier t=
hat attack is - just simultaneously DoS a bunch of nodes, perhaps by a lo=
w-bandwidth exploit like the bloom io or division by zero DoS attacks. Th=
is is much harder to pull off if every SPV client is passing around block=
 headers.

Similarly by passing around full blocks the attacker has a harder time kn=
ocking other miners off the network. Regardless of whether or not a miner=
's peers are fully validating chain data they still have the data they ne=
ed to mine the next block and thus extend the longest correct chain.
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