Seed anatomy
Words are an encoding, not the source.
Move between every BIP39 length and watch source entropy plus checksum bits pack into 11-bit word indexes.
12 words contain 128 source entropy bits and 4 checksum bits.
12 words carry 128 source bits.
The checksum adds 4 error-detection bits. It can reject many mistyped phrases; it cannot prove the source was unpredictable.
Source entropy128 bitsmust come from generation
Checksum4 bitsderived from the entropy
Encoded total132 bits12 indexes × 11 bits
word 1word 2word 3word 4word 5word 6word 7word 8word 9word 10word 117E + 4C
The last word is mixed.
For this length, its 11-bit index contains 7 entropy bits and 4 checksum bits. Calling it “the checksum word” hides that distinction.
This uses numbered, non-secret tiles. It does not generate, validate, or display a recovery phrase.