First of all you are better off not using this for random addresses that have a lot of money, because their difficulty is ASTRONOMICALLY GREATER (you probably don't need a lecture about this) than an address with specialized information about it like the puzzle transaction.

As for getting public keys associated with the addresses, this is only possible if there is at least one transaction associated with the address, which'll always be the cease if you're talking about funded addresses. Use blockchain.info to find a transaction involving the address you want to run Kangaroo on, then copy the transaction ID and paste it into blockstream.info, select the "Details" button, and under the address there will be a bunch of of information at "scriptsig (asm)", where you will find the public key there.

We need two block explorers to accomplish this because Blockchain doesn't show public keys, and Blockstream can't search by address.


Don't bother trying to brute force this, it's in a hot wallet that was included in the block mined just now. It'll definitely move somewhere else later.

That red underlined hex number is the public key for the address that Blockstream's block explorer shows.