Long time ago, several users of this forum suggested to punish double-spends by burning the amount:
https://bitcointalk.org/index.php?topic=3168https://bitcointalk.org/index.php?topic=3441.msg49447#msg49447https://bitcointalk.org/index.php?topic=208167.20https://bitcointalk.org/index.php?topic=54746.0If a miner can come up with a new signed TX including an input already used as input in the previous block he can claim the input as an additional transaction fee.
The TX in the previous block becomes invalid!
Transactions that only changed the transaction fee must be excluded.
There are just two possible outcomes:
1) Merchant receives their money. Buyer payed merchant.
2) Merchant receives nothing. Miner receives payment. Buyer payed miner.
There is no penalty for the buyer but also no incentive. I think that should be enough.
This change makes single confirmation TXs less secure than now but removes the incentive to double spend. With the current system I don't see a use case for single confirmation TXs other than preventing double spends anyway. TXs with two or more confirmations are as secure as today.
A problem is that it is necessary to make 100% sure never to broadcast modified TXs (with the exception of increased fees).
Even Gavin Andresen played with the idea:
Again, it seems to me some rules that make attempted double-spends more costly to those who attempt to pull off double-spends might be a good idea.
Is there any altcoin out there that applies a penalty in case of double-spend attempts? Do you know of any research papers about the topic?
