HOW TO FUCK UP DICE ROLLS
The scenario we're considering is someone using a ColdCard to create a new Bitcoin seed with dice rolls. The question is, what can go wrong?
TOO FEW ROLLS
The simplest thing that can go wrong is entering too few dice rolls. For a fair die, 50 rolls is the minimum. 100 is plenty. If you only roll 20 times, your wallet will be at risk.
HUMAN LAZINESS
The most common way people screw up dice rolls is human laziness. People get bored halfway through and start mashing buttons or trying to "invent" random numbers in their heads, which drastically reduces entropy.
UNFAIR DICE
An unlikely thing to go wrong would be using wildly unfair die. A purist would recommend using casino dice, which are intentionally balanced, but many people will just use any available game dice.
A fair die encodes 2.585 bits of entropy per roll. Suppose your die so weighted that it NEVER lands on 6. In that case, you've only got log2(5) = 2.322 bits per roll.
At 50 rolls, you have 2.322 x 50 = 116.1 bits total. This is BELOW the minimum 128 bits required.
However, our hypothetical unfair die, rolled 100 times, produces 232.2 bits of entropy, which is ABOVE the 128-bit threshold. So even an unfair die can produce sufficient entropy if rolled enough times.
DATA ENTRY FAILURE
Hypothetically, the user could enter the values incorrectly. The buttons on a ColdCard are not always easy to press. Someone could roll the dice 100 times but fail to register some rolls, which would reduce the total entropy.
MENU SYSTEM FAILURE
Hypothetically, the user could fail to use the feature correctly. Maybe they got to the screen for entering dice rolls, entered all the numbers, but then hit BACK rather than proceeding to lock it in.
SUPPLY CHAIN ATTACK
Even if you do everything perfectly, you’re trusting the device.
One could imagine a scenario where the ColdCard had been physically tampered with (a supply chain attack) so that no matter what you enter for your dice rolls, it produces a seed the attacker already knows. A similar attack successfully drained funds from fake Trezor devices. While I haven't heard of it happening to a ColdCard, it's in the realm of possibility. https://www.kaspersky.com/blog/fake-trezor-hardware-crypto-wallet/48155/%5D(https://www.kaspersky.com/blog/fake-trezor-hardware-crypto-wallet/48155/
Those are the main failure points off the top of my head. I hope this helps!
