> For Bitcoin, the most popular one, on the order of 100.000.000.000.000.000.000 of hashes get calculated to mine a single block, multiple trillion per second. Within ten minutes, only a single one of those 100.000.000.000.000.000.000 hashes is actually used, depending entirely on luck. The rest are thrown away entirely. They do not form part of the final hash or anything else, the energy spent on them is lost.
All of those hashes and the energy required to generate them represent work that would need to be redone (along with all subsequent work) by an attacker in order to double-spend the transactions in that block. It's the most efficient way to use energy for security that there is.
Not really, it's secured by Proof of Violence/Imprisonment in partnership with the country's government. And the government spends a lot more energy doing that than bitcoin does
We need the state monopoly on violence in order to maintain an orderly society, regardless of which monetary system we use. The energy used by law enforcement to secure the financial system is a tiny fraction of the total, and switching from fiat currency to cryptocurrency wouldn't reduce that energy use at all.
The banking system has zero security for you as an individual. The DB admins though? They do enjoy some security. (Still not as much as Bitcoin, having central points of failure.)
Have you ever had a fraudulent credit card transaction? I've had at least 5 over the last 30 years including some for over $2,000. I call the credit card company, tell them this wasn't me, the charge gets removed, they cancel my card and send me another in 3 days. In the last 10 years their fraud monitoring has gotten good enough that they see something suspicious and block the transaction. Then they email, text, and call asking to verify if this was really me.
All of those hashes and the energy required to generate them represent work that would need to be redone (along with all subsequent work) by an attacker in order to double-spend the transactions in that block. It's the most efficient way to use energy for security that there is.