Roll your own bitcoin entropy.
Use a fair physical six-sided die. Every roll stays on this device.
1. Choose phrase length
Locks after the first roll24 words uses 256 bits. Confirm your intended wallet accepts this phrase length before funding it.
2. Enter each roll
Press 1–6 after each physical roll
Rolls live in this tab’s memory only—never in storage, a URL, analytics, or the clipboard. The complete sequence is as secret as the phrase. Leaving or refreshing clears it; a browser warning is requested but cannot be guaranteed.
3. Reveal recovery phrase
Locked until at least 100 physical rolls are recorded for 24 words.
Uniform sample accepted
Your entropy is ready.
The checksum catches some transcription mistakes. It does not add secret entropy.
- Physical rolls
- 100
- Entropy
- 256 unbiased bits
- Format
- 24-word BIP39 English
Your recovery phrase
Write each numbered word by hand, in order.
Phrase hidden during check
Check your paper backup.
Enter the requested words from paper. This spot-check never reveals an expected word.
Six-position spot-check passed
Your paper backup matched.
This is not a complete wallet recovery test. Test restoration in the intended wallet before receiving funds.
Session cleared
Active roll and phrase state was released.
JavaScript cannot promise forensic memory erasure. The app never used storage or the clipboard. Destroy the complete paper roll tally after your recovery phrase is safely backed up—it can recreate the phrase.
Know what the tool proves—and what it cannot.
Unbiased math, safe display, accurate backup, and successful wallet recovery are four separate checks.
How bias is removed
Six-sided dice ranges do not always divide evenly into a power of two. Entropy Key accepts only an evenly mappable range. If the sequence lands in the leftover range, it recycles that entropy and asks for another physical roll.
How BIP39 words are made
The accepted entropy receives a short SHA-256 checksum, then the combined bits are split into 11-bit indexes for the embedded 2,048-word English BIP39 list. The checksum is error detection, not extra entropy.
What this tool cannot protect against
A compromised browser, extension, operating system, keyboard, screen recorder, app build, or physically biased die can still undermine the result. This creates a recovery phrase—not a wallet, account, address, or optional BIP39 passphrase.
Why there is no “randomness score”
Repeated faces and long runs are valid. A small sample cannot prove a die is fair, and selectively rejecting patterns would add human bias. Record every physical result exactly as rolled.