Seed Generator Built with Dice and a Calculator

I’ve been into Bitcoin for about 9 years now. In my second year, I bought a Ledger Nano S, and it served me well. Just about when I was running out of storage on the Nano S, the Nano S Plus was released, which I used happily up until recently.

I run my own node and mempool, and I’ve been using a multisig wallet set up with my Ledgers. During the Amazon Prime Day sale last June, I picked up a Trezor Safe 3 and a Blockstream Jade, and upgraded my multisig setup using hardware from different vendors.

Then came the recent Coldcard drama… which inspired me to build my own seed generator using dice roll.

I knew that SeedSigner could generate a seed from D6 dice rolls, so I tried building one with a Raspberry Pi I had lying around. Unfortunately, I didn’t have the right screen for it, so that plan fell through.

After giving it some thought, I realized I could just use the Python feature on my Casio calculator to build one. I coded it up, and it actually works perfectly! ^^

P.S.
This program was built using the MicroPython built into modern Casio graphing calculators. Instead of using any built-in dice tool on the calculator, you roll actual physical dice 99+ times and sequentially input the results via the keypad. The program then performs a SHA-256 operation, handles checksum padding and 11-bit slicing according to BIP39 standards, and generates a 24-word mnemonic. Since MicroPython is stripped down to the bare essentials and lacks a built-in hashlib, I actually had to implement the SHA-256 algorithm from scratch. This program brings the physical dice-based entropy generation found in devices like Coldcard, SeedSigner, and Keystone Pro right onto a graphing calculator!