That's what makes this much harder, we are not looking for a string, we are looking for a (random) number.
Given the length and complexity of the previous puzzle, do you think this one would be so simple?
You're probably not looking for a private key. You're probably looking for the IP of a minecraft server - or ANYTHING else...

the puzzle started with other clues and
ended with this last clue, as coin_artist has stated the painting contains the key, not the next step to the key. read this thread from the beginning to see this puzzle has already dragged on for 6 months.