Subject: Re: [Bitcoin-development] blind symmetric commitment for stronger byzantine voting resilience (Re: bitcoin taint & unilateral revocability)

From: Caleb James DeLisle <[email-masked]>
Date: Wed, 15 May 2013 08:40:59 -0400

I can't see this working, if 51% of the mining power doesn't like your
coins, when you create the commitment they will reject it.
If the commitment is opaque at the time of inclusion in the block then
I will create multiple commitments and then after revealing the
commitment and spend to you I will reveal the earlier commitment which
commits the coins to an address I control.

On the topic of reversibility, I suspect in the long term the lack of
chargebacks will create issues as criminals learn that for the first
time in history, kidnap & ransom is effective. Suffice to say after the
first >= $10mn kidnapping-for-bitcoin heist, governments will be forced
to decide how they view the system. It will likely fall somewhere between
"arrest/question anyone identified holding tainted coins" to something
nonsensical and reactionary like "blocking" bitcoin as Iran does TOR.

Thanks,
Caleb

On 05/15/2013 07:49 AM, Adam Back wrote:
> On Wed, May 15, 2013 at 07:19:06AM -0400, Peter Todd wrote:
>> Protocols aren't set in stone - any attacker that controls enough
>> hashing power to pose a 51% attack can simply demand that you use a
>> Bitcoin client modified [to facilitate evaluation of his policy]
> 
> Protocol voting is a vote per user policy preference, not a CPU vote, which
> is the point.  Current bitcoin protocol is vulnerable to hard to prove
> arbitrary policies being imposable by a quorum of > 50% miners.  The blind
> commitment proposal fixes that, so even an 99% quorum cant easily impose
> policies, which leaves the weaker protocol vote attack as the remaining
> avenue of attack.  That is a significant qualitative improvement.
> 
> The feasibility of protocol voting attacks is an open question, but you
> might want to consider the seeming unstoppability of p2p protocols for a
> hint.
> 
> Adam
> 
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