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About BIP39 Mnemonic Generation
BIP39 mnemonic sentences are generated using a specific process to ensure security and consistency:
- Initial entropy (128-256 bits) is generated.
- A checksum is created by taking the first ENT/32 bits of the SHA256 hash of the entropy.
- The checksum is appended to the entropy.
- The result is split into 11-bit groups, each corresponding to a word from a 2048-word list.
The relationship between entropy (ENT), checksum (CS), and mnemonic sentence length (MS) is:
CS = ENT / 32
MS = (ENT + CS) / 11
For a 12-word mnemonic (most common), this means:
- 128 bits of entropy
- 4-bit checksum
- 132 bits total, split into 12 11-bit words
The difficulty of guessing a valid mnemonic increases exponentially with the number of missing words. For each missing word, there are 2048 possibilities, but only a fraction will produce a valid checksum.
This calculator estimates the number of valid combinations and provides examples, helping to illustrate the security of BIP39 mnemonics.
For more informations, refer to: https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki