An Air-Gapped BIP39 Calculator for Crypto Seed Generation

Before a hardware wallet can protect your cryptocurrency, it needs a seed phrase. Most wallets generate that phrase automatically, leaving users to trust that the device produced truly random words and handled them securely. Seedmate focuses entirely on that first step. Rather than generating a seed behind the scenes, the handheld device lets users create, verify, and manipulate BIP39 seed phrases offline using randomness they can see and provide themselves.

Seedmate is a dedicated, air-gapped BIP39 calculator. It never connects to a computer, smartphone, or the internet, and there is no USB data interface, wireless radio, or companion application. Once the power switch is turned off, the device retains nothing in memory, making it completely stateless.

The hardware is very minimal (📷: Seedmate)

Instead of asking users to trust a random number generator, Seedmate accepts entropy from the physical world. Dice rolls, coin flips, playing cards, or even words selected by hand can all be converted into a valid 12- or 24-word BIP39 mnemonic. One particularly interesting mode allows users to randomly choose 24 words themselves, with the device modifying only the final word so the checksum is correct. The remaining words stay exactly as they were chosen, and every calculation is displayed for manual verification.