Discussion thread here: https://bitcointalk.org/index.php?topic=1306983.msg64526037#... Bitcoin puzzles are private keys with just a few unknown bits so that anyone can bruteforce them to collect a reward. Puzzle 66 contained 66 unknown bits and had 6.6 BTC deposited into it by the initial puzzle creator. The private key was 0x000000000000000000000000000000000000000000000002832ed74f2b5e35ee or 256 bits with mostly ze…
Curious to know because I've never looked into this stuff: doesn't the _public_ key have to be available anyway so you can send the coins to the address in the first place and have that recorded on the ledger?
This is one of the reasons it is advised never to reuse an address. After using it once, your private key may still be private but your public key is exposed, reducing security.