Subject: Re: [Bitcoin-development] BIP proposal - patch to raise selfish mining threshold.

From: Alessandro Parisi <[email-masked]>
Date: Tue, 5 Nov 2013 19:18:22 +0100

Patrick, could you please explain us why the solution proposed by Ittay
would drop the actual honest miners ratio, becoming so backfire? Thanks a
lot

2013/11/5 Patrick <[email-masked]>

>  The ratio of honest miners that mine the first block they see is > 0.5
>
> Your proposed solution would reduce that ratio to 0.5
>
> In other words your proposed change would make the attack you describe
> easier not harder.
>
>
> On 11/05/2013 09:26 AM, Ittay wrote:
>
> That sounds like selfish mining, and the magic number is 25%. That's the
> minimal pool size.
> Today the threshold is 0% with good connectivity.
>
>  If I misunderstood your point, please elaborate.
>
>  Ittay
>
>
>
> On Tue, Nov 5, 2013 at 12:05 PM, Peter Todd <[email-masked]> wrote:
>
>> On Tue, Nov 05, 2013 at 11:56:53AM -0500, Ittay wrote:
>> > Hello,
>> >
>> > Please see below our BIP for raising the selfish mining threshold.
>> > Looking forward to your comments.
>>
>>  <snip>
>>
>> > 2. No new vulnerabilities introduced:
>> > Currently the choice among equal-length chains is done arbitrarily,
>> > depending on network topology. This arbitrariness is a source of
>> > vulnerability. We replace it with explicit randomness, which is at the
>> > control of the protocol. The change does not introduce executions that
>> were
>> > not possible with the old protocol.
>>
>>  Credit goes to Gregory Maxwell for pointing this out, but the random
>> choice solution does in fact introduce a vulnerability in that it
>> creates incentives for pools over a certain size to withhold blocks
>> rather than immediately broadcasting all blocks found.
>>
>> The problem is that when the pool eventually choses to reveal the block
>> they mined, 50% of the hashing power switches, thus splitting the
>> network. Like the original attack this can be to their benefit. For
>> pools over a certain size this strategy is profitable even without
>> investing in a low-latency network; Maxwell or someone else can chime in
>> with the details for deriving that threshold.
>>
>> I won't get a chance to for a few hours, but someone should do the
>> analysis on a deterministic switching scheme.
>>
>> --
>> 'peter'[:-1]@petertodd.org
>> 0000000000000005e25ca9b9fe62bdd6e8a2b4527ad61753dd2113c268bec707
>>
>
>
>
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