Entropy
Entropy is the measure of randomness or unpredictability used in generating cryptographic keys and seed phrases. High-quality entropy ensures that your Bitcoin private keys cannot be guessed or reproduced. Without sufficient entropy, your keys are fundamentally insecure regardless of all other precautions.
How It Works
When you generate a new Bitcoin wallet, the process starts with a random number. A standard 12-word BIP39 seed encodes 128 bits of entropy; a 24-word seed encodes 256 bits. If the input is unpredictable, the search space is too large to brute-force. If it is weak or biased, the words can look normal while the wallet remains guessable.
Hardware wallets normally generate entropy internally. Better designs combine independent sources, check for failures, and let the owner add a private contribution that the device does not control.
Bring Your Own Entropy
Use a supported on-device flow that mixes independent device entropy with physical input you control. Dice rolls, coin flips, and unpredictable key-press timing can add a second source without asking you to trust your own input alone.
On current COLDCARD firmware, the standard new-seed flow combines the hardware generator and both secure elements with one required user method: at least 65 unpredictably timed key presses, 50 rolls of a real six-sided die, or 128 flips of a real coin. For dice or coins, use the physical object again for every entry. Do not use an app, website, saved list, or invented pattern.
Treat the input as secret. Keep the device away from cameras and never record the complete sequence. If you use an advanced dice-only workflow instead, the dice become the only entropy source: a 24-word seed requires at least 99 fair, independent rolls. That is different from adding 50 supplemental rolls to the standard mixed-entropy flow.
Do not choose BIP39 words yourself or enter a short sequence and assume hashing makes it strong. Use the wallet's documented method and understand whether your input is mixed with device entropy or replaces it.
Key Points
- 12-word seeds encode 128 bits of entropy; 24-word seeds encode 256 bits
- Prefer a supported flow that mixes independent device entropy with private physical input
- Supplemental input and dice-only seed generation are different workflows
- Flawed random number generators have caused real-world Bitcoin losses
- Never invent words or patterns, use an online generator, or record the complete entropy sequence