This is just to verify my understanding of Bitcoin double spend detection.
1) Use of UTXO indexes : This ensures that there as been no spend from that output (transferred to recipient in Block of height N) in any of the subsequent transactions, up till last confirmed Block in chain (from N till current height). So the binary search if UTXO indexes is necessarily done for all transactions, right?
2) A con could theoretically double spend by garnering enough (51%) computing power to generate longer blocks that don't include his first (legit) spend', and pay himself or partner with from same output (since smaller length with legit transaction would be rejected). But this is only a theoretical possibility. right?
2) A wait of 6 confirmed blocks is recommended for high value transactions, as it is less likely for your confirmed transaction to get dropped from chain after that, even if con has upto 10% computing power. right ?