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List:       bitcoin-dev
Subject:    Re: [bitcoin-dev] proposal: new opcode OP_ZKP to enable ZKP-based spending authorization
From:       ZmnSCPxj via bitcoin-dev <bitcoin-dev () lists ! linuxfoundation ! org>
Date:       2023-05-06 2:51:33
Message-ID: -ZXduH8kzOVdK_FBE0VvMtuKDAFSU0Z4joKeIqM7CFnHO9kymMHfVwGjlwEHLzAnFWXLd_jVtNrkdeQGVobYUqjwASXEQ2w8BHh5FtEMJzs= () protonmail ! com
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Good Morning Weiji,


> Hi ZmnSCPxy,
> > As the network is pseudonymous, an anonymous attacker can flood the fullnode \
> > mempool network with large numbers of non-aggregated transactions, then in \
> > cooperation with a miner confirm a single aggregated transaction with lower \
> > feerate than what it put in the several non-aggregated transactions.
> 
> Arguably this is hardly a feasible attack. Let's suppose the attacker creates 1000 \
> such transactions, and attaches each transaction with a small amount of transaction \
> fee X. The total fee will be 1000*X collectible by the aggregation vendor, who pays \
> the miner a fee Y. We can reasonably assume that 1000*X is much larger than Y, yet \
> X is much smaller than Y. Note that Y is already much larger than the regular fee \
> for other transactions as the aggregated transaction should contain many inputs and \
> many outputs, thus very large in size. 
> Now, the attacker will have to generate proofs for these 1000 transactions, which \
> is non-trivial; and pay for 1000*X upfront. The aggregation vendor has to spend \
> more computing power doing the aggregation (or recursive verification) and take \
> (1000*X - Y) as profit. Miner gets Y.

The entire point is that there has to be a separate, paid aggregator, in order to \
ensure that the free mempool service is not overloaded. Basically, keep the \
aggregation outside the mempool, not in the mempool. If aggregation is paid for, that \
is indeed sufficient to stop the attack, as you noted.

Regards,
ZmnSCPxj
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