We have some taproot address with private key "a" and public key "a*G", owned
by Alice. Bob wants to take Alice's coins without her permission. He owns
taproot address with private key "b" and public key "b*G". He knows "a*G" by
exploring the chain and looking for P2TR outputs. To grab Alice's funds, he
creates "(b-a)*G" taproot address and send some small amount to this address.
Then, Bob can create a transaction with two inputs, taking coins from "a*G" and
"(b-a)*G" addresses. All that is needed is producing a signature matching the
sum of the public keys used in taproot, which is "(a+b-a)*G", reduced to "b*G",
so Bob uses his "b" private key to produce Schnorr signature. Is there any
protection from this attack?
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