So you are claiming that any Bitcoin transaction could be double-spended and therefore all Bitcoin transactions are insecure. Makes sense ?
What do you think of a challenge? I transfer an amount of x coins, you only know the source address, which I will publish here. Its private key will be in the range of 66bit just like the mentioned puzzle. Then you siphon off the coins and transfer them to another address before I receive them just like you described the looter would. If the coins end up at your freely chosen address, you can keep them. If they end up with me, you have lost and made a fool of yourself. Deal ?
@Legends_Never_Die
So what's about the RBF-challenge, deal or no deal?I generate an address with a 66bit private key and send a few coins to it. Then I create a transaction to send the entire contents of this wallet address to any other address. I will explicitly set 1 sat/vB as the fee so that the transaction can stay in the blockchain forever. Now you (or someone else if you like) try to cancel this outgoing transaction and thus simulate a mallory sucker that wants to withdraw the coins. As the transaction has the minimum fee you have all the time that you need.
As the fees are currently very high, I am unfortunately unable to send coins to the RBF-challenge address. If anyone is interested in this RBF-challenge and would like to sponsor some minimum amount of satoshis, here is the wallet address:
1C8uD9G4AGQas5sG15869p5B1mrF3RELY3I own the private key of this address
The sha256 of the privkey is:
6297b7a9a38985d967e9d5603ba5e4f133b0e8a998219f29c4029aa03601110b
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Using a 66-bit private key is like to do a transaction, and few seconds after make the private private key "public".
Retrieving such private key from a public key is matter of time with a GPU.
A suggestion for your challenge:
1) choose an address where you have already a few satoshi
2) make a tx with fee = 1 satoshi
3) public here a range of 2^66 range in which your private keys is
It the same challenge, but you save a tx.