[bitcoin-dev] BIP suggestion: PoW proportional to block transaction sum

Darren Weber dweber.consulting at gmail.com
Wed Jun 6 21:01:22 UTC 2018

Hi Thomas,

Thanks for considering this suggestion.  You've raised some interesting
points (and concluded that it could be very difficult to implement).  I'm
not yet at a point where I could answer any questions about implementation
details with any authority.  With that caveat, your points are worth
considering further and I will dwell on it for a bit.

Best regards,

On Tue, Jun 5, 2018 at 3:50 AM, Thomas Guyot-Sionnest <dermoth at aei.ca>

> On 30/05/18 12:17 PM, Darren Weber via bitcoin-dev wrote:
> >
> > Apologies for brevity, noob here and just throwing out an idea in case
> > it's useful (probably already covered somewhere, but I haven't got
> > time to do all the necessary background research).
> >
> > From https://github.com/bitcoin/bitcoin/issues/13342
> >
> > Suggestion:  To make it more difficult for a malicious attacker to
> > reap quick rewards by double-spending large amounts with a relatively
> > brief majority of the network hashing power, introduce a hash workload
> > that is proportional to the sum of transactions in a block (probably
> > the sum of the absolute values, and a "proportionality function" could
> > be linear or exponential).  The motivation is to make it more
> > difficult for malicious attacks to hash-power their way through a few
> > large transactions.  Obviously, there are costs in greater transaction
> > delays (and fees?) for larger amounts (absolute value).
> >
> > If there is original value in the idea, I can try to make time to
> > follow-up with a better BIP proposal.
> >
> Hi Darren,
> I'm wondering how do you think this can be implemented... The problem
> being that you cannot just decide to exclude transactions because you
> found a lesser difficulty hash since that hash includes all transactions
> already... Miners will either include or not these transactions based on
> economical value, and since most of the rewards still comes from block
> rewards there would be very little right now except with very high fees.
> Even worse, it may have detrimental side-effects: since there is no
> distinctions between destination and change addresses, one can only
> assume the transaction amount is the full input amount. Therefore users
> would be inclined to keep large amount in lots of smaller addresses to
> avoid being penalized on small transactions, increasing the UTXO size
> for everybody.
> And besides, this is a huge change to swallow, requiring very good
> consensus and a hard fork. IMHO I wouldn't even waste time on this.
> Regards,
> --
> Thomas

Darren L. Weber, Ph.D.
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