Re: [Bitcoin-development] Bitcoind-in-background mode for SPV wallets

[Peter Todd <pete@petertodd.org>]

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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℅ of hashing power the next step for them to attack SPV clients is to 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 that attack is - just simultaneously DoS a bunch of nodes, perhaps by a low-bandwidth exploit like the bloom io or division by zero DoS attacks. This 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 knocking 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 need to mine the next block and thus extend the longest correct chain.
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