Great question. If your dice are fair, 100 is way more than enough. 50 is the real minimum threshold.
To assert that those rolls produce that seed, you need two devices from different manufacturers running the same algorithm.
For example, the algorithm ColdCard uses has been reproduced in Python. You could put the rolls into your ColdCard, write down the words, then put the same rolls into a computer and run the Python program to see that it yields the same words.
Of course, now you have a new problem: your seed has touched a general purpose computer. So ideally, you would use one that is eternally quarantined and has never touched the Internet.
Or, you can find another signing device manufacturer that uses the same algorithm. SeedSigner might. I’m not sure.
You can see now why just rolling dice is not the panacea that people make it out to be.
