it is pretty simple. think of it as base 6, write the codes like
12345256234232162342123523415123512362341
off the top of my head, it's gonna need to be a lot to reach equal to 2^128. nah i'm gonna give you exact numbers:
50 dice rolls to get 128 bits, 100 dice rolls gives you 256. 50 is the minimal, if you are serious about this you roll 100 times. and i'd recommend also using several different dice, all made different ways, stone, plastic, big, little. plenty of board games use them, i know some at least have a tumbling mechanism that is quite convenient
