On Wed, Jul 15, 2015 at 12:32 PM, Peter Todd <pete@petertodd.org> wrote:

"In a Sybil attack the attacker subverts the reputation system of a
peer-to-peer network by creating a large number of pseudonymous
identities, using them to gain a disproportionately large influence."

Our "identities" aren't pseudonymous.

In the case of Bitcoin, there's something like 6,000 nodes, so if that
20% is achived via outgoing connections you'd have 600 to 1200 active
outgoing connections using up network resources.  Meanwhile, the default
is 8 outgoing connections - you're using about two orders of magnitude
more resources.

You're not talking about a Sybil attack anymore, just resource use. We do know how to change default configurations to offer more connections.

If you are achieving that via incoming connections, you're placing a big
part of the relay network under central control. As we've seen in the
case of Chainalysis's sybil attack, even unintentional confirguation
screwups can cause serious and widespread issues due to the large number
of nodes that can fail in one go. (note how Chainalysis's actions were
described(1) as a sybil attack by multiple Bitcoin devs, including
Gregory Maxwell, Wladimir van der Laan, and myself)

We're not Chainanalysis and we do not run hundreds of distinct nodes. Just a few well-tuned ones.
 
What you are doing is inherently incompatible with decentralization.

That's a matter of opinion. One could argue your actions and control attempts hurt decentralization. Either way, no one should play the decentralization police or act as a gatekeeper.

Question: Do you have relationships with mining pools? For instance, are
you looking at contracts to have transactions mined to guarantee
confirmations?

No, we do not. We do not know anyone else having such contracts. As you know, Coinbase also denied having such contracts in place [1]. But you seem to have more relationships with mining pools than we do.

Thanks,
Matthieu
CTO and Founder, BlockCypher

[1] http://lists.linuxfoundation.org/pipermail/bitcoin-dev/2015-June/008864.html