From: Jonas Schnelli <dev@jonasschnelli.ch>
Message-Id: <4EC6599E-D317-4E4F-9E4D-37B7006B8C15@jonasschnelli.ch>
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Date: Wed, 29 Aug 2018 20:27:51 +0200
In-Reply-To: <758E3CA7-295B-4B77-BFF5-9AAE959D53EA@voskuil.org>
To: Eric Voskuil <eric@voskuil.org>
References: <CA+9w0-77oP3rmW37R6ty4fF_LhaOtQaL52yQUKynXEmZhQ9MeA@mail.gmail.com>
	<8AE1517F-88FB-479D-AE89-993A5545D210@jonasschnelli.ch>
	<758E3CA7-295B-4B77-BFF5-9AAE959D53EA@voskuil.org>
Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>,
	Blockchain Group <shekharhiran@gmail.com>
Subject: Re: [bitcoin-dev] Building a Bitcoin API and query system.
Precedence: list


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> The API implementation is not what is centralizing, nor is full =
indexation non-scalable. The centralization is in not running the API =
from a node under your own control. This is of course implied by the =
comment, =E2=80=9Cwithout the need for syncing=E2=80=9D. In other words =
it is the deployment cost of the node that is centralizing.

IMO an API that serves non verifiable data is supporting centralised =
validation. The =E2=80=9EAPI" which supports one of the most important =
properties in Bitcoin =E2=80=93 the ability to self-validate =E2=80=93 =
is the data available via the p2p network.

>=20
> Yet if people relied only on bitcoind and never centralized services =
there would be *no* block explorers (and no secure light wallets), =
because it does not provide remote query and does not fully index.
>=20
> Block explorers and light wallets are pretty useful, so presumably =
some API must provide these features (ideally with reduced deployment =
cost). That will either be centralized or decentralized services. As =
such it seems wise to encourage the latter, as opposed to questioning =
whether there is any valid block explorer use case.

Bitcoin-Core has all required features to partially =E2=80=9Eindex=E2=80=9C=
 data (called the wallet) and provides them via the RPC API. If you =
don=E2=80=99t need to serve thousands of wallets (which smells after =
centralised validation), selective indexing (wallets) are the right =
choice. Also, if you have a proper light client architecture, you can =
use Bitcoin Core in pruned mode (<10GB of data) to serve an endless =
amount of wallets (client/server mode, I guess that is what you are =
referring to with "light clients").

I fail to see the use-cases where a fully index blockchain makes sense =
(the only one I can come up with is instant backup recovery where the =
transaction history needs to be preserved rather then recovering the =
UTXOs only).

Also, the p2p protocol has built in light client support with BIP37 =
(bloom filters) and soon BIP158 will be available on the network which =
does allow privacy-preserving "light clients" in a way where no trusted =
layer is required (client <-> p2p network rather then client <-> API =
provider <-> p2p network).

I don=E2=80=99t want to advocate against a full-index blockexplorer-like =
API. I just think its important to define the use case and be aware of =
the consequences and downsides.

/jonas

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