[bitcoin-dev] A Small Modification to Segwit

Jorge Timón jtimon at jtimon.cc
Sun Apr 9 11:48:27 UTC 2017


Why won't the attacker use asicboost too? (Please don't say because of
patents)

On 9 Apr 2017 12:26 am, "Jimmy Song" <jaejoon at gmail.com> wrote:

> Jorge,
>
> Suppose someone figures out an ASIC optimization that's completely
> unrelated that gives X% speed boost over your non-ASICBoosted
> implementation. If you ban ASICBoost, someone with this optimization can
> get 51% of the network by adding N machines with their new optimization. If
> you allow ASICBoost and assuming this gets a 20% speed boost over
> non-ASICBoosted hardware, someone with this optimization would need 1.2N
> machines to get 51%. The network in that sense is 20% stronger against this
> attack in terms of cost.
>
> Jimmy
>
> On Sat, Apr 8, 2017 at 12:22 PM, Jorge Timón <jtimon at jtimon.cc> wrote:
>
>> To be more specific, why "being higher will secure the Bitcoin network
>> better against newer optimizations"?
>> Or, to be more clear, let's forget about future "optimizations", let's
>> just think of an attacker. Does asicboost being used by all miners
>> make the system more secure against an attacker? No, for the attacker
>> can use asicboost too.
>> What about the case when not all the miners are using asicboost? Then
>> the attacker can actually get an advantage by suing asicboost.
>>
>> Sometimes people compare asicboost with the use of asics in general as
>> both providing more security for the network and users. But I don't
>> think this is accurate. The existence of sha256d asics makes an attack
>> with general purpose computing hardware (or even more specialized
>> architectures like gpgpu) much more expensive and unlikely. As an
>> alternative the attacker can spend additional resources investing in
>> asics himself (again, making many attacks more expensive and
>> unlikely).
>>
>> But as far as I know, asicboost can be implemented with software
>> running on general purpose hardware that integrates with regular
>> sha256d asics. There is probably an advantage on having the asicboost
>> implementation "in the same box" as the sha256d, yet again the
>> attacker can invest in hardware with the competitive advantage from
>> having asicboost more intergrated with the sha256d asics too.
>>
>> To reiterate, whether all miners use asicboost or only a subset of
>> them, I remain unconvinced that provides any additional security to
>> the network (to be more precise whether that makes "tx history harder
>> to rewrite"), even if it results on the hashrate charts looking "more
>> secure".
>>
>>
>> On Sat, Apr 8, 2017 at 6:27 PM, Jorge Timón <jtimon at jtimon.cc> wrote:
>> >
>> >
>> > On 8 Apr 2017 5:06 am, "Jimmy Song via bitcoin-dev"
>> > <bitcoin-dev at lists.linuxfoundation.org> wrote:
>> >
>> > Praxeology Guy,
>> >
>> >> Why would the actual end users of Bitcoin (the long term and short term
>> >> owners of bitcoins) who run fully verifying nodes want to change
>> Bitcoin
>> >> policy in order to make their money more vulnerable to 51% attack?
>> >
>> >
>> > Certainly, if only one company made use of the extra nonce space, they
>> would
>> > have an advantage. But think of it this way, if some newer ASIC
>> optimization
>> > comes up, would you rather have a non-ASICBoosted hash rate to defend
>> with
>> > or an ASICBoosted hash rate? Certainly, the latter, being higher will
>> secure
>> > the Bitcoin network better against newer optimizations.
>> >
>> >
>> > Why?
>>
>
>
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