First, some background knowledge — bitcoins are a form of cryptocurrency that can be stored in "addresses". Each bitcoin address is linked to a specific private key. To access bitcoins in a specific address, a person needs a private key in order to do so. To put simply — for each bitcoin address (analogous to a bank account), there is a corresponding private key (analogous to a password) to unlock and access the bitcoins.
Now, let's say some genius finds a previously unknown mathematical method to crack private keys faster than brute force. Can he legally claim bitcoins for himself by doing the following?
He deliberately finds bitcoin addresses that have been dormant for years (indicating that it is very possible that their owners have lost their keys and are unable to access the coins. Lost bitcoins are very common - approximately 20% of all bitcoins in existence are lost.), and hacks their private keys.
He transacts the coins to a custodial address first.
He then sends a message to the hacked address and informs the owners that he has found their bitcoins, and requests that the owner claim them within a specific time period.
Once the deadline is up, and no one shows up to claim the coins, he takes them for himself.
In this case, would the "finders keepers" law apply? Meaning that if I find someone else's money, I try to inform the owner and no one shows up to claim the money, I can basically take the money for myself.
I'm asking this question because there is a group known as the "Large Bitcoin Collider" who is trying to brute force other people's private keys and claim the funds for themselves. According to the group, it will give the original owner six months to claim the funds before the group takes the money for themselves, which is "in accordance with European laws." Is this actually legal? (See here)