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From: Eric Voskuil <eric@voskuil.org>
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Subject: Re: [bitcoin-dev] BIP 151
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Hi Alfie,
Yes, this is exactly what I meant. The complexity of the proposed constructi=
on is comparable to that of Bitcoin itself. This is not itself prohibitive, b=
ut it is clearly worthy of consideration.
A question we should ask is whether decentralized anonymous credentials is a=
pplicable to the authentication problem posed by BIP151. I propose that it i=
s not.
The core problem posed by BIP151 is a MITM attack. The implied solution (BIP=
151 + authentication) requires that a peer trusts that another is not an att=
acker.=20
Authentication of an anonymous peer cannot achieve this objective, since the=
peer may be anyone and an attack on privacy can be undetectable. The identi=
ty of a peer must be known to the relying peer, either directly or transitiv=
ely.
DAC is applicable in cases where identity is never required. The prime exam=
ple in the paper is that of first-come-first-served name registration. No id=
entity is required in that scenario, just proof that a party in question is t=
he original registrant. All participants are presumed to be "good".
I believe that a distributed anonymous system is fundamentally at odds with i=
solation of "good" vs. "bad" participants who comply with protocol rules (Do=
S considerations aside), and that any attempt to resolve this conflict will r=
esult in the system no longer allowing anonymous participation.
I may be mistaken, but I haven't found a way out of this realization.
e
> On Jun 29, 2016, at 1:17 PM, Alfie John <alfie@alfie.wtf> wrote:
>=20
> On Tue, Jun 28, 2016 at 06:45:58PM +0200, Eric Voskuil via bitcoin-dev wro=
te:
>>> then we should definitively use a form of end-to-end encryption between
>>> nodes. Built into the network layer.
>>=20
>> Widespread application of this model is potentially problematic. It is a
>> non-trivial problem to design a distributed system that requires authenti=
cation
>> but without identity and without central control. In fact this may be mor=
e
>> challenging than Bitcoin itself. Trust on first use (TOFU) does not solve=
this
>> problem.
>=20
> Maybe the following paper can feed into this discussion:
>=20
> "Decentralized Anonymous Credentials" by Christina Garman, Matthew Green, I=
an Miers
> https://eprint.iacr.org/2013/622.pdf
>=20
> Alfie
>=20
> --=20
> Alfie John
> https://www.alfie.wtf
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