Physical BIP39 Seed Generator

Standalone offline checksum calculator · open source · no dependencies

Generate entropy with a physical die

Use a fair six-sided die. Roll independently: 1, 3, 5 → 0; 2, 4, 6 → 1. Record every roll in order. Use exactly 128 rolls for 12 words or 256 rolls for 24 words. Do not pick patterns, discard unwanted rolls, or reuse rolls for another wallet. This tool cannot detect biased dice.

The calculator hashes your entropy with SHA-256, appends the first 4 or 8 checksum bits, and divides the result into 11-bit word indices (0–2047). Look up those indices on the poster. The last word includes entropy and checksum; it cannot be chosen freely.

Print or save the full dictionary as PDF. Choose A1 portrait for the numbered poster. Each index starts at 0 and includes its 11-bit binary value.

English has the widest wallet compatibility. Confirm your wallet supports the chosen language. Never translate a generated phrase. Changing the instruction language does not change the dictionary.

Leave blank for no passphrase. This changes the public key, not the seed words. Case and spaces matter. Keep a separate backup of the exact passphrase.

Worked example · 12 words

Public example only. Never use this phrase for funds or copy this predictable roll pattern for a real wallet.

Example input: 128 rolls, each showing 1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

With the English dictionary selected, 128 rolls of 1 produce 128 zero bits. SHA-256 gives checksum bits 0011. The first eleven 11-bit groups have index 0; the last group is 00000000011, index 3. The result is eleven instances of “abandon”, followed by “about”. This example always uses the English dictionary, regardless of your current selections.

Example recovery phrase · English dictionary

abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon about

Back up on paper

Write all 12 or 24 words in exact order, numbered. Check every word and verify recovery with a trusted offline wallet before depositing funds. Keep the paper private, dry and secure; consider a second secure location. Do not photograph, upload, email or share it. Back up an optional passphrase separately. Clear the input and close the file when finished; clearing cannot guarantee erasure from device memory.

Private entropy and generated phrases are excluded from printing.

Generate random seed

Standard entropy: generate 128 or 256 bits with the browser’s cryptographic random source, then calculate a 12- or 24-word BIP39 phrase using the selected dictionary. Use a trusted offline device. This replaces any entered rolls or bits.

github.com/zuyux/utxo · github.com/bitcoin/bips/blob/master/bip-0039.mediawiki · MIT License

https://github.com/bitcoin/bips/tree/master/bip-0039